Critical slowing down and topological freezing severely hinder Monte Carlo sampling of lattice field theories as the continuum limit is approached. Recently, significant progress has been made in applying a class of generative machine learning models, known as "flow-based" samplers, to combat these issues. These generative samplers also enable promising practical improvements in Monte Carlo...
We report on our on-going study of the $B_s \to K\ell\nu$ decay in $N_f=2+1$ lattice QCD. The M\"obius domain-wall action is employed for all quark flavors at a lattice cutoff of $a^{-1} \sim 2.5$ GeV. We present preliminary results for the relevant form factors extracted from correlator ratios by inspecting their ground state saturation.
Upon taking a bosonic quantum field theory in the Hamiltonian formalism and discretizing the field on a lattice, the theory becomes equivalent to a non-relativistic many-body problem. Neural networks have recently been proposed as effective wavefunction parametrizations in numerical searches for ground state solutions of quantum many-body problems using variational Monte Carlo. We introduce a...
We update our calculation of flavor diagonal nucleon axial, scalar and tensor charges on eight 2+1+1-flavor MILC HISQ ensembles using Wilson-clover fermions. We discuss the signal in the sum of the connected and disconnected contributions for the up, down and strange quarks, control over fits to remove excited state contamination, the simultaneous chiral-continuum fit used to extract the...
We discuss implementations of lattice gauge theories on digital quantum computers. In particular, we investigate the number of gates required to simulate the time time evolution. Using state-of-the art methods with our own augmentation, we find that the cost of simulating a single time step evolution of an elementary plaquette is prohibitive in the current era of quantum hardware. Moreover, we...
A previous calculation of baryon-baryon scattering using CLS ensembles with nonperturbatively $O(a)$-improved Wilson fermions revealed large discretization effects in the scattering amplitude. It is natural to ask whether other systems with heavy hadrons are affected. Using the same setup and adding valence charm quarks with the same action, we study $DD^*$ scattering and the $T_{cc}$...
The SU(3) gauge theory with $N_f=10$ fundamental flavors is thought to be close to the sill of the conformal window. I describe a recent study of this system using the continuous $\beta$ function method based on the gradient flow. We use a Pauli-Villars improved gauge action and several gradient flow transformations. These features allow us to study the system at much stronger gauge...
We present results of a study of spontaneous symmetry breaking through fermion bilinear condensation in the single flavor Thirring Model in 2+1$d$. Domain Wall Fermions are used to capture the symmetry breaking pattern U(2)$\to$U(1)$\otimes$U(1) in the limit of domain wall separation $L_s\to\infty$, with the conserved fermion current coupled to a real vector auxiliary field defined throughout...
We discuss the properties of Quantum Chromodynamics at finite temperature obtained by means of lattice simulations with the overlap fermion discretization. This fermion discretization preserves chiral symmetry even at finite lattice spacing. We present the details of the formulation and discuss the properties of the chiral thermal phase transition. We compare the results obtained with the...
Quantum chromodynamics (QCD) which is the theory of strong interactions describes the thermodynamics of strongly interacting matter at finite temperatures and densities. At low temperatures, chiral symmetry is broken in the QCD vacuum and as temperature increases, a transition occurs where chiral symmetry is restored, resulting in the formation of the quark gluon plasma (QGP). It is found that...
We use the continuous renormalization-group method, based on the gradient flow, to study a candidate theory of composite Higgs and a partially composite top. The model is an SU(4) gauge theory with four Dirac fermions in each of the fundamental and two-index antisymmetric representations. Our lattice action includes a set of Pauli-Villars fields, which decouple in the continuum limit while...
We perform a lattice simulation to investigate the doubly charm tetraquark $T^+_{cc}$ observed by the LHCb collaboration with flavor content $cc\bar{u}\bar{d}$, isospin-$0$, and only $0.4$ MeV below the $D^{*+}D^0$ threshold. We implement two-meson interpolators, and additionally also diquark-antidiquark interpolators. This is the first extraction of the scattering amplitude from correlators...
The RBC & UKQCD collaborations have successfully employed G-parity boundary conditions in the measurement of $K\to\pi\pi$ decays to obtain a physical decay with the two-pion ground state, at the cost of a significant increase in computational expense. We report on new theoretical/algorithmic developments based upon the properties of the Dirac operator under complex conjugation that have been...
We present a trainable framework for efficiently generating gauge configurations, and discuss ongoing work in this direction. In particular, we consider the problem of sampling configurations from a 4D $SU(3)$ lattice gauge theory, and consider a generalized leapfrog integrator in the molecular dynamics update that can be trained to improve sampling efficiency.
The axial charge of the nucleon, $g_A$, has been computed extensively on the lattice. However, the axial charges for other octet baryons (hyperons) such as the $\Sigma$ and $\Xi$ baryons are less well known experimentally and theoretically.
Here we present results for the isovector axial, scalar and tensor charges, as well as for the second Mellin moments of isovector PDFs. This allows us...
In this study, we investigate the real-time dynamics in the $(1+1)$d U(1) gauge theory called the Schwinger model via variational quantum algorithms. Specifically, we simulate the quench dynamics in the presence of the external electric field.
We first prepare the ground state in the absence of the external field using variational quantum eigensolver (VQE) and then perform the real-time...
Heavy-light semileptonic decays provide an important channel to perform high-energy precision tests of the standard model, determine $|V_{ub}|$, and test lepton flavour universality. In this talk, the current status of exclusive $B_s\to K\ell\nu$ semileptonic decays within the RBC-UKQCD Relativistic Heavy Quark (RHQ) project will be presented. We will present recently-published form factor...
We present calculations of the complex potential at non-zero temperature in 2+1 flavor QCD.
The complex potential is obtained from spectral reconstruction of the Wilson line correlators
at non-zero temperature calculated on the lattice. The calculations are performed using the HISQ
action at three lattice spacings, a=0.028 fm, a=0.04 fm and a=0.049 fm for temperatures in the range
130 MeV...
The doubly charmed tetraquark $T_{cc}^+$ recently discovered by the LHCb collaboration is studied on the basis of (2 + 1)-flavor lattice QCD simulations of $D^*D$ system with nearly physical pion mass $m_\pi = 146$ MeV. The interaction of $D^* D$ in the isoscalar and $S$-wave channel, derived from the hadronic spacetime correlation by the HAL QCD method, is attractive for all distances and...
We present results from the QCDSF/UKQCD/CSSM collaboration for the charges g_T, g_A and g_S of the baryon octet, obtained through the use of Feynman-Hellmann techniques. We use a flavour symmetry breaking method to systematically approach the physical quark mass using ensembles that span five lattice spacings and multiple volumes. We extend this existing flavour breaking expansion to also...
We compute the complete set of form factors for the $B\to \pi$, $B\to K$, and $B_s\to K$ amplitudes, which are needed to describe semileptonic $B$-meson decay rates for both the charged and neutral current cases. We use the highly improved staggered quark (HISQ) action for the sea and light valence quarks. The b quark is described by the Wilson-clover action in the Fermilab interpretation....
Symmetric mass generation (SMG) is a new mechanism that leads to massive bound states without spontaneous symmetry breaking. An SMG phase could lead to a resolution of the chiral fermion problem on the lattice. Expectations from 't Hooft anomaly cancellation, combined with recent finite-size scaling results, indicate that the SU(3) gauge-fermion system with two sets of staggered fermions could...
Effective String Theory (EST) is a non-perturbative framework used to describe confinement in Yang-Mills theory through the modeling of the interquark potential in terms of vibrating strings. An efficient numerical method to simulate such theories where analytical studies are not possible is still lacking. However, in recent years a new class of deep generative models called Normalizing Flows...
State preparation is a crucial aspect of quantum simulation of quantum field theories. When aiming to simulate Standard Model physics, it is likely that fault-tolerant quantum computers will be required. In this regime, it is beneficial to consider algorithms that exhibit nearly optimal scaling with the problem parameters. Many of these algorithms rely on repeated calls to a block encoding of...
When calculating hadronic matrix elements using a lattice regulator,
the presence of power divergences in the lattice spacing poses a significant challenge.
Non-perturbatively subtracting these power divergences presents
both theoretical and numerical difficulties.
The gradient flow offers a theoretically sound and numerically robust approach
for renormalizing power divergences.
We...
I discuss a model-independent framework for fitting hadronic
form-factor data, which is often only available at discrete
kinematical points, using parameterisations based on unitarity and
analyticity. The accompanying dispersive bound on the form factors
(unitarity constraint) is used to regulate the ill-posed fitting
problem and allow model-independent predictions over the...
The renormalization group beta function describes the running of the renormalized coupling, connects the ultraviolet and infrared regimes of quantum field theories, and characterizes the nature of gauge-fermion systems. Using the concept of the continuous beta function and renormalized couplings obtained from the gradient flow, we present results for SU(3) gauge theories with $N_f=2$, 4, 6, 8,...
The order of finite temperature QCD phase transition on the lower left corner of Columbia plot is yet to be determined, and the current studies show that the bound of critical mass has a strong cutoff and discretization scheme dependence. We present an update on the QCD phase transition with 3 flavors of Möbius domain wall fermions at zero chemical potential. We performed simulations on...
The digital quantum simulation of lattice gauge theories is expected to become a major application of quantum computers. Measurement-based quantum computation is a widely studied competitor of the standard circuit-based approach. We formulate a measurement-based scheme to perform the quantum simulation of Abelian lattice gauge theories in general dimensions. The scheme uses an entangled...
A lot of progress has been made in the direct determination of nucleon sigma terms. Using similar methods we consider the sigma terms of the other octet baryons as well. These are determined on CLS gauge field ensembles employing the Lüscher-Weisz gluon action and the Sheikholeslami-Wohlert fermion action with $N_\mathrm{f} = 2 + 1$. The ensembles analysed here have pion masses ranging from...
Calculations of topological observables in lattice gauge theories with traditional Monte Carlo algorithms have long been known to be a difficult task, owing to the effects of long autocorrelations times. Several mitigation strategies have been put forward, including the use of open boundary conditions and methods such as parallel tempering. In this contribution we examine a new approach based...
The study of doubly heavy tetraquarks has gained substantial topical interest, primarily boosted by the recent discovery of doubly charmed tetraquark $T_{cc}$ and by its phenomenological prospects. While $T_{cc}^+$ is observed to be $\sim$0.4 MeV below the $DD^*$ threshold, multiple lattice calculations point to a deep binding ($\mathcal{O}(100 MeV)$) in $T_{bb}$. However, the predictions for...
The measurements of nucleon Electric Dipole Moments (EDMs) are important to probe CP violation and physics beyond the Standard Model. In this talk, I will report our recent progress in calculating nucleon theta EMDs using background electric field. We extract neutron EMDs by measuring the energy shift of 2pt correlation function in the presence of background field. The gauge ensembles are...
Lattice gauge-equivariant convolutional neural networks (LGE-CNNs) can be used to form arbitrarily shaped Wilson loops and can approximate any gauge-covariant or gauge-invariant function on the lattice. Here we use LGE-CNNs to describe fixed point (FP) actions which are based on inverse renormalization group transformations. FP actions are classically perfect, i.e., they have no lattice...
In this talk, we present preliminary results on $\pi\pi$ and $\rho\rho$ coupled-channel scattering with 4 degenerate light quark flavors. We focus on different scattering channels, two of which are attractive and possess the same quantum numbers as the two $X_{0,1}(2900)$ tetraquark candidates recently discovered at LHCb. Using Luscher's formalism, we investigate these resonances in the...
We present results from our lattice QCD study of the contribution of the isovector quark chromo-electric dipole moment (qcEDM) operator to the nucleon electric dipole moments (nEDM). The calculation was carried out on four 2+1+1-flavor of highly improved staggered quark (HISQ) ensembles using Wilson-clover quarks to construct correlation functions. We use the non-singlet axial Ward identity...
We present recent progress on the lattice calculation of semileptonic form factors for $B \to D^{\ast} \ell \nu$ decay using linear fit method. We use the Oktay-Kronfeld (OK) action for the charm and bottom valence quarks. We use results of 2pt correlator fit of $B$ and $D^{\ast}$ meson as input parameters to the data analysis on the 3pt correlation functions. Here, the masses of charm and...
Based on simulations of 2+1 flavor lattice QCD with M\"obius domain wall fermions at high temperatures, we use a series of recently developed spatial correlation functions to study the screened masses for quarks in meson bound states. We compare these screened masses with the symmetries of the correlators using a pair of fitting ansatz for various quark masses and lattice sizes with...
The origin of the infinite volume based beta-function from the gradient flow is discussed with its technical implementations. Recent applications include the new beta function with ten massless fermion flavors in the SU(3) color representation and the new effort to calculate with high precision the QCD running coupling at the $Z$~pole.
We report preliminary results from an analysis of the pion scalar form factor computed on a set of the $\mathrm{tr}[M]=\mathrm{const}$ CLS gauge ensembles with $N_f=2+1$ Wilson Clover-improved sea quarks. The calculations are carried out for light quarks masses corresponding to $M_\pi\approx 0.130\mathrm{MeV} \ldots 350\mathrm{MeV}$, four values of the lattic spacing...
We study the $U(1)_A$ anomaly at high temperatures of $N_f=2+1$ lattice QCD with chiral fermions. Gauge ensembles are generated with M\"obius domain-wall (MDW) fermions, and in the measurements, the determinant is reweighted to that of overlap fermions. We report the results for the Dirac spectra, the $U(1)_A$ susceptibility, and the topological susceptibility at temperatures, T=136, 153, 175,...
Traditionally, there has been a method to analyze the charge radius of the hadron based on the fits of its form factor with some model assumptions. Moreover, a completely different method has been proposed, which does not depend on the models. In this presentation, we explore several improvements to this model-independent method for analyzing the pion charge radius. Furthermore, we compare the...
In this talk we present a lattice determination of the hadronic susceptibilities that, as a consequence of unitarity and analyticity, constrain the form factors entering the semileptonic $b\rightarrow c$ transitions. We evaluate the longitudinal and transverse susceptibilities of the vector, axial and tensor polarization functions at zero momentum transfer from the moments of appropriate...
Speaker: Prof. Robert Shrock
Institution: Stony Brook University
Title: Higher-Order Calculations of Anomalous Dimensions at
Infrared Fixed Points in Gauge Theories and Studies of Renormalization-Group
Behavior of Some Scalar Field Theories
Abstract
We discuss higher-order calculations of anomalous dimensions of
operators at an infrared fixed point in asymptotically free...
Neutrinoless double beta decay is a hypothetical beyond the Standard Model (BSM) process that, if observed, would imply that neutrinos are Majorana particles. Interpreting the results of double beta decay experiments requires knowledge of nuclear matrix elements that are calculable with lattice QCD. This talk presents determinations of the long-distance (mediated by a light Majorana neutrino)...
TEK reduction is a well established technique that allows single-site simulations of Yang-Mills theory in the large-$N_c$ limit by exploiting volume reduction induced by twisted boundary conditions. We performed simulations for $SU(841)$ for several gauge couplings and applied standard Wilson flow techniques combined with a tree-level improvement methodology to set the lattice scale. The wide...
We present an update for results on B-meson semileptonic decays using the highly improved staggered quark (HISQ) action for both valence and 2+1+1 sea quarks. The use of the highly improved action, combined with the MILC collaboration’s gauge ensembles with lattice spacings down to ~0.03 fm, allows the b quark to be treated with the same discretization as the lighter quarks. The talk will...
To conquer topological freezing in gauge systems, we develop a variant of trivializing map proposed in Luecher 2019. We in particular consider the 2D U(1) pure gauge model, which is the simplest gauge system with topology. The trivialization is divided into several stages, each of which corresponds to integrating local degrees of freedom, the decimation, which can be seen as coarse-graining....
Hamiltonian truncation is a quantum variational method that approximates the ground state by minimizing the energy on a finite truncated basis of Hilbert space. A straightforward application of this method to quantum field theory would seem to be hopeless, since generic states in the Hilbert space have an exponentially small overlap with physical states. Nonetheless, this talk will present...
I give a status update for the Grid Python Toolkit software project.
The Hamiltonian formulation of lattice QCD with staggered fermions in the strong coupling limit can be extended to 2 flavors. It has no sign problem at non-zero baryon density and isospin densities and allows for Quantum Monte Carlo simulations. We have implemented a Quantum Monte Carlo algorithm to measure the baryon and isospin densities in the $\mu_B$ - $\mu_I$ plane in the chiral limit. We...
Qubit regularization provides a framework for studying gauge theories through finite-dimensional local Hilbert spaces, presenting opportunities for digital quantum simulations. In this talk, we investigate the IR phases of 2d QCD with the $\mathrm{SU}(N)$ gauge group via qubit regularization. In the continuum, a 2d $\mathrm{SU}(N)$ gauge theory coupled to a single flavor of fundamental...
Scale separation is an important physical principle that has previously enabled algorithmic advances such as multigrid. Previous work on normalizing flows has been able to utilize scale separation in the context of scalar field theories, but mostly not in the context of gauge theories. In this talk, I will give an overview of a new method for generating gauge fields using heirarchical...
We investigate QCD at large isospin density by computing correlation functions between sources with isospin charge $n=1,\ldots,6144$ on two lattice volumes at quark masses corresponding to a pion mass, $m_\pi\sim170$ MeV. By extracting the energies of the corresponding many-pion systems under the assumption of log-normality of the correlation function distributions, we determine the isospin...
We calculate the leading-order QED corrections to meson masses and bare quark masses. As lattice QCD calculations become more precise, these QED corrections are becoming more important. However, one of the challenges in adding QED effects to QCD calculations is avoiding power-law suppressed finite volume effects. These effects can enter calculations of many observables because QED has massless...
The rise of exascale supercomputers has fueled competition among GPU vendors, requiring lattice QCD practitioners to write code that supports multiple GPU architectures and APIs. We present SIMULATeQCD, a simple multi-GPU lattice code for large-scale QCD calculations, mainly developed and used by the HotQCD collaboration. Our open source code is built on C++ and MPI, includes CUDA and HIP...
I will present preliminary results of next-generation lattice-QCD calculations of the $\Lambda_b \to p$, $\Lambda_b \to \Lambda$, and $\Lambda_b \to \Lambda_c$ form factors based on RBC/UKQCD gauge-field ensembles with 2+1 flavors of domain-wall fermions. Compared to the work published in 2015 and 2016, the new calculations include three additional ensembles (one with 139 MeV pion mass, one...
We present preliminary results for the large-$N$ limit of the chiral condensate
computed from twisted reduced models. We followed a two-fold strategy, one constiting in extracting the condensate from the quark-mass dependence of the pion mass, the other consisting in extracting the condensate from the mode number of the Dirac operator.
We present a new way of computing the pion screening mass at finite isoscalar chemical potential $\mu_\ell$, starting from the Taylor expansion of the screening correlator in $\mu_\ell$. The method derives from the known exact expression for the free theory pion screening correlator at finite $\mu_\ell$. As a first check of the formalism, we compare the lattice results for the free theory...
Other than the commonly used Wilson’s regularization of quantum field theories (QFTs), there is a growing interest in regularizations that explore lattice models with a strictly finite local Hilbert space, in anticipation of the upcoming era of quantum simulations of QFTs. A notable example is Euclidean qubit regularization, which provides a natural way to recover continuum QFTs that emerge...
In the rapidly changing hardware landscape of high performance computing (HPC), binding workforce to optimize simulation software for just a single architecture becomes a sustainability issue.
In this work I explored the feasibility of using performance portable parallel code for a staggered fermion kernel. Fusing the Kokkos C++ Performance Portability EcoSystem with MPI allows to scale on...
The chiral condensate is computed from the mode number of the staggered Dirac operator. This result is compared with those obtained with other approaches, based on the quark mass dependence of the topological susceptibility and of the pion mass.
State-of-the-art simulations of discrete gauge theories are based on Markov chains with local changes in the field space, which however at very fine lattice spacings are notoriously difficult due to separated topological sectors of the gauge field resulting in very long autocorrelation times.
An approach, which can overcome long autocorrelation times, is based on trivializing maps, where a...
Recent experimental progress measuring the branching fractions of the heavy-baryon semileptonic decays $\Xi_c \to \Xi \ell \nu$ have stimulated theoretical interest and motivate precise lattice calculations of the form factors. Here we present such a calculation using domain-wall fermions for the up, down, and strange quarks, and an anisotropic clover action for the charm quark. We use four...
We give an update on an ongoing project in which we calculate the masses of octet and decuplet baryons including isospin-breaking effects. To this end, we employ single- and two-state-fits to effective masses at leading and sub-leading order in the expansion in isospin-breaking parameters. In order to remove objective bias on asymptotic masses we furthermore compute an AIC-based model-average...
We present a study on the nonperturbative calculation of observables for inclusive semileptonic decays of $B_{(s)}$-mesons using lattice QCD. We focus on the comparison of two different methods to analyse lattice data of Euclidean correlation functions and address inverse problems, specifically Chebyshev and Backus-Gilbert approaches. This type of computation may eventually provide new insight...
We determine the location of the critical point where the first-order deconfining transition in the heavy-quark region turns into a crossover in finite-temperature and density QCD with 2+1 flavors. Combining a hopping parameter expansion of the quark determinant with a reweighting method, we evaluate the chemical potential dependence of the critical point. By systematically calculating the...
In this presentation, we will discuss the application of recent and emerging C++ features, with a focus on portable parallel programming in lattice QCD. Specifically, the discussion will center around certain key features introduced in the C++17, C++20, and C++23 standards, as well as an exploration of some experimental features currently under development.
A primary emphasis will be placed...
We present mechanisms to constrain fermionic condensates on the level of the path integral, which grant access to the quantum effective potential in the infinite volume limit. In the case of a spontaneously broken symmetry this potential possesses a manifestly flat region, which is usually inaccessible to the standard approach of a double limit of volume and explicit symmetry breaking. By...
We show how multigrid preconditioners for the Wilson-clover Dirac operator can be constructed using gauge-equivariant neural networks. For the multigrid solve we employ parallel-transport convolution layers. For the multigrid setup we consider two versions: the standard construction based on the near-null space of the operator and a gauge-equivariant construction using pooling and subsampling...
We consider gauge theories on a four-dimensional torus, where the instanton number is restricted to an integral multiple of $p$. This theory possesses the nontrivial higher-group structure, which can be regarded as a generalization of the Green-Schwarz mechanism, between the $1$-form center and $\mathbb{Z}_p$ $3$-form symmetries. Following recent studies of the lattice construction of the...
The $\Lambda(1405)$ resonance is listed in PDG as a strangeness $S=-1$ baryon with quantum numbers $I(J^P)=0(\frac{1}{2}^-)$. However, most models based on chiral effective theory and unitary suggest two nearby overlapping resonance poles. This two-pole picture for the $\Lambda(1405)$ is disputed by recent phenomenological fits to experimental data which require only a single pole, and...
Effective string theory has shown its universal power in the prediction of the spectrum of low-lying excited states of confining strings. In these works we focus on 3d Ising gauge model and vector $Z_N$ gauge theories. We have computed the low-lying confining flux tube spectrum in 3d Ising gauge model and shown that they agree with the prediction of the Nambu-Goto spectrum. Moreover, we...
The Bielefeld Parma Collaboration has in recent years put forward a method to probe finite density QCD by the detection of Lee Yang singularities. The location of the latter is obtained by multi-point Padè approximants, which are in turn calculated matching Taylor series results obtained from Monte Carlo computations at (a variety of values of) imaginary baryonic chemical potential. The method...
Tackling ever more complex problems of non-perturbative dynamics requires simulations and measurements on ever increasingly large lattices at physical quark masses. In the age of the exascale, addressing the challenges of ensemble generation and measurements at such scales requires a plethora of algorithmic advances, both in theory space and in the implementation space. In this talk we will...
We extend the definition of L\"uscher's lattice topological charge to the case
of $4$d $SU(N)$ gauge fields coupled with $\mathbb{Z}_N$ $2$-form gauge fields.
This result is achieved while maintaining the locality, the $SU(N)$ gauge
invariance, and $\mathbb{Z}_N$ $1$-form gauge invariance, and we find that the
manifest $1$-form gauge invariance plays the central role in our...
I will give a status update of using OpenMP target offloading in the Grid library. As part of the US Exascale Computing Project, we have been investigating the possibility of using a portable programming model in Grid to support execution on different architectures. OpenMP, a directives-based programming model, supports both CPU multithreading and different GPU architectures through...
We report on the progress in the analysis of the inclusive semi-leptonic decay of the $D_s$ meson. This analysis is based on a pilot simulation conducted for the $D_s \rightarrow X_s \ell\nu$ process where we employed Möbius domain-wall charm and strange quarks whose masses were tuned to be approximately physical and where we covered the whole kinematical region.
The focus of this talk is to...
We perform a numerical study in lattice QCD on $\Lambda(1405)$, an excited $\Lambda$ baryon whose existence is not well explained by the quark model. Since the previous studies using the chiral unitary model suggest that $\Lambda(1405)$ may be explained by two poles in the octet and the singlet channels of the flavor SU(3), we calculate the HAL QCD potentials for the meson-baryon systems in...
I will present ongoing efforts, by the Budapest-Marseille-Wuppertal collaboration, concerning the staggered-fermion computation of the HVP two-point function, on new 0.048 fm lattices. In particular, I will focus on aspects of our GPU determination of the Omega baryon mass, used for scale setting, and that of the connected, light-quark contribution to the muon g-2.
One possible approach to the quantum simulation of gauge theories involves replacing the gauge group, a compact Lie group, with one of its discrete finite subgroups. We show how the electric Hamiltonian may be interpreted as a Laplacian operator on the finite group and how this is related to the degeneracy of the electric ground state. Moreover, we discuss the dimension of the physical,...
We solve the long-standing problem concerning the fate of the chiral $U(1)_A$
symmetry in QCD-like theories at high temperature in the chiral limit. We
introduce a simple instanton based random matrix model that precisely
reproduces the properties of the lowest part of the lattice overlap Dirac
spectrum. We show that in the chiral limit the instanton gas splits into a
free gas component...
We present results for the electromagnetic form factors of the proton and neutron computed on the $(2 + 1)$-flavor Coordinated Lattice Simulations (CLS) ensembles including both quark-connected and -disconnected contributions. The $Q^2$-, pion-mass, lattice-spacing, and finite-volume dependence of our form factor data is fitted simultaneously to the expressions resulting from covariant chiral...
We present updated results of the excited and exotic spectra of $B, B_s$ and $B_c$ mesons. The calculations are performed on dynamical, anisotropic lattices with relativistic heavy quarks. A first look at finite volume effects and next steps are also discussed.
I derive a formulation of the 2-dimensional critical Ising model on non-uniform simplicial lattices. Surprisingly, the derivation leads to a set of geometric constraints that a lattice must satisfy in order for the model to have a well-defined continuum limit. I perform Monte Carlo simulations of the critical Ising model on discretizations of a 2-sphere and I show that the simulations are in...
We determine the scales $r_0$, $r_1$, and the ratio $r_0/r_1$ for 2 + 1 flavour QCD ensembles generated by CLS. These scales are determined from an improved definition of the static force which we measure using Wilson loops and furthermore use to study the shape of the static potential. Our analysis involves various continuum and chiral extrapolations of data that covers pion masses between...
Suzuki-Trotter decompositions of exponential operators like exp(Ht) are required in almost every branch of numerical physics. Often the exponent under consideration has to be split into more than two operators, for instance as local gates on quantum computers.
In this talk, I will demonstrate how highly optimised schemes originally derived for exactly two operators can be applied to such...
Hamiltonian simulations of quantum systems require a finite-dimensional representation of the operators acting on the Hilbert space. Here we present a discretization scheme for gauge links and canonical momenta of an SU(2) gauge theory which offers the possibility to freely refine the discretisation. This is achieved by discretising SU(2) and constructing the canonical momentum using the...
We use the method of optimal distillation profiles to compute the low-lying charmonium spectrum in an $N_f = 3+1$ ensemble at the $SU(3)$ light flavor symmetric point ($m_{\pi} \approx 420$ MeV), physical charm quark mass and lattice spacing $a\approx 0.0429$ fm. The spectrum and mass splittings display good agreement with their values in nature and the statistical errors are comparable, if...
We perform a finite-size scaling analysis of the critical point in the heavy-quark region of QCD at nonzero temperature. Our previous analysis at $N_t=4$ is extended to a finer lattice with $N_t=6$ and $8$. The aspect ratio is also extended up to 18 to suppress the non-singular contribution. High-precision analysis of the Binder cumulant is realized by an efficient Monte-Carlo simulation with...
We present results of nucleon structure studies measured in 2+1 flavor QCD with the physical light quarks in a large spatial extent of about 10 fm. Our calculations are carried out with the PACS10 gauge configurations generated by the PACS Collaboration with the stout-smeared $O(a)$ improved Wilson fermions and Iwasaki gauge action at $\beta$=1.82 and 2.00 corresponding to the lattice spacings...
A general geometrical framework is explored for quantum field theory on curved manifolds motivated by the recent map of the 2d Ising model on a triangulated grid to reproduce the integrable conformal field theory (CFT) on the modular torus ($\mathbb T^2$) and the Riemann sphere ($\mathbb S^2$). This talk will emphasize the special role of affine transformations as a bridge between...
Lattice QCD with Wilson quarks near the continuum limit can be described by Symanzik's effective continuum action which contains the dimension 5 operator, $m \,tr(F_{\mu\nu}F_{\mu\nu})$. Its effect can be eliminated by an O$(am)$ rescaling of the bare lattice coupling constant.The corresponding improvement coefficient, $b_g$, is currently only known to 1-loop order and the resulting...
I review the status of the RBC/UKQCD g-2 program with focus on updates for the hadronic vacuum polarization.
We will investigate the effectiveness of tuning HMC parameters using
information from the gradients of the HMC acceptance probability with
respect to the parameters. In particular, the optimization of the
trajectory length and parameters for higher order integrators will be
studied in the context of pure gauge and dynamical fermion actions.
We present an update, from the Fermilab Lattice, HPQCD, and MILC collaborations, of our results for the hadronic vacuum polarization contribution to the muon’s anomalous magnetic moment. Preliminary results for light-quark-connected contributions to the intermediate and long-distance window quantities employ new, low-mode-improved, data sets on our finest ensembles. We also present updated...
We present a first numerical implementation of a massive nonperturbative renormalisation scheme, RI/mSMOM, in the study of heavy quarks using the domain-wall fermion action. In particular, we calculate renormalisation constants for fermion bilinears at non-vanishing heavy quark masses and compare the approach to the continuum of the renormalised charm quark mass with that from a...
At its critical point, the three-dimensional Ising model is described by a conformal field theory (CFT), the 3d Ising CFT. While the critical exponents of the Ising model, which are related to the scaling dimensions of certain primary operators of the CFT, have been well-investigated in lattice calculations over the past few decades, the theory’s operator product expansion (OPE) coefficients...
The deconfinement transition in QCD is understood as the spontaneous breaking of $\mathbb{Z}_N$ symmetry at high temperatures. Accordingly, quark-gluon plasma generally includes some partial cells called center domains, each with a homogeneous Polyakov-loop. In this work, constructing an effective action describing the deconfinement vacuum of QCD with $N$ colors, we discuss the properties of...
The Deep Underground Neutrino Experiment (DUNE) is an upcoming neutrino oscillation experiment that is poised to answer key questions about the nature of the neutrino. Lattice QCD has the ability to make significant impact upon DUNE by computing the interaction of a nucleon to a weak current. Nucleon amplitudes involving the axial form factor are part of the primary signal measurement process...
It has been demonstrated that distillation profiles can be employed
to build optimized quarkonium interpolators for spectroscopy calculations
in lattice QCD. We test their usefulness for heavy-light systems on
(3+1)-flavor ensembles with mass-degenerate light and a charm quark in
the sea in preparation for a future DDbar-scattering analysis.
The additional cost of light inversions...
Numerical simulations of quantum Hamiltonians can be done representing the degrees of freedom as matrices acting on a truncated Hilbert space. Here we present a formulation for the lattice $SU(2)$ gauge theory in the so called "magnetic basis", where the gauge links are unitary and diagonal. The latter are obtained from a direct discretization of the group manifold, while the canonical momenta...
We introduce nested sampling as a generic simulation technique to integrate over the space of lattice field configurations and to obtain the density of states. In particular, we apply it as a tool for performing integrations in systems with ergodicity problems due to non-efficient tunneling, e.g., in case of topological freezing or when computing first order phase transitions. As a proof of...
Experimentally many exotic charmonium-like mesons have already been discovered, for example, the $Z_c$ mesons. We study the spectrum of such states with isospin 1 focusing on the $\bar cc \bar qq$ channels with $J^{P}=1^{+}$, $C=\pm$. This is the first study of four-quark states with these quantum numbers, where the total momentum is non-zero. The simulations are performed on two...
In the hybrid Monte Carlo simulation of $\mathrm{SU}(3)$ pure gauge theory, we explore a Fourier acceleration algorithm to reduce critical slowing down. By introducing a soft-gauge-fixing term in the action, we can identify the eigenmodes in the weak-coupling expansion of the action and eliminate the differences in their evolution frequencies. A special unit-link boundary, in which the links...
The current status of lattice-QCD numerical calculations by joint LHP and RBC collaborations of nucleon isovector vector- and axialvector-current form factors using a 2+1-flavor dynamical domain-wall fermions lattice QCD ensemble generated jointly by RBC and UKQCD collaborations will be presented. The lattice spacing is set at about 0.1141(3) fm, and the lattice spatial extent is 48 spacings...
We describe how the general mechanism of partial deconfinement applies to large-N QCD and the partially-deconfined phase inevitably appears between completely-confined and completely-deconfined phases. Furthermore, we propose how the partial deconfinement can be observed in the real-world QCD with SU(3) gauge group. We propose how the Polyakov loop and chiral condensate should behave and test...
Simulations of bosonic field theories on quantum computers demand a truncation in field space to “fit” the theory onto limited quantum registers. We examine two different truncations preserving the same symmetries as the 1+1-dimensional $O(3)$ non-linear $\sigma$-model - one truncating the Hilbert space of functions on the unit sphere by setting an angular momentum cutoff and a fuzzy sphere...
Dynamical Triangulations might provide a tool to discover asymptotic safety in quantum gravity. This scenario is based on scale invariance which is realized at an interacting fixed point of the renormalization group flow. In this spirit, asymptotically safe quantum gravity is a quantum field theoretic approach to quantum gravity. On the lattice, asymptotic safety would be realized as a...
In this study we employ staggered fermions to calculate the two-pion taste singlet states at rest. Leveraging the Clebsch-Gordan coefficients of the symmetry group associated with staggered fermions, we effectively compute the $\pi\pi$ contributions to the resting $\rho$-meson. To discern the distinct energy states involved, we adopt a generalized eigenvalue problem-solving approach. This work...
We report on the ongoing effort of improving the determination of the gradient flow scale on the 2+1+1 HISQ ensembles generated by the MILC collaboration. We measure the $t_0$ and $w_0$ scales with the Wilson and Symanzik flow using three discretizations for the action density: clover, Wilson and tree-level Symanzik-improved. For the absolute scale setting we intend to employ the Omega baryon...
As several lattice collaborations agree on the result for the
window quantity of the hadronic vacuum polarization (HVP) contribution to
(g-2)_\mu, whilst being in tension with the calculation using the dispersive
approach, further effort is needed in order to pin down the cause for this
difference.
Here we investigate the isospin breaking corrections to the leading order HVP.
In...
We carry out a scale setting procedure of a mixed action setup
consisting of valence Wilson twisted mass fermions at maximal twist on
CLS ensembles with $N_f=2+1$ flavours of $O(a)$-improved Wilson sea
quarks. We determine the gradient flow scale $t_0$ using pion and kaon
isoQCD masses and decay constants as external input. We employ model
variation techniques to probe the systematic...
I will discuss a discretization of Euclidean, weak-field General Relativity allowing the generation of a Markov chain of dynamic, pure gravity spacetimes at non-zero temperature via Metropolis algorithm with importance sampling. A positive action conjecture is implemented on the lattice, ensuring a probabilistic interpretation of exp(-S) and that dS=0 yields the Einstein field equations....
The effect of a finite volume presents itself both in heavy ion experiments as well as in recent model calculations. The magnitude is sensitive to the proximity of a nearby critical point. We calculate the finite volume effects at finite temperature in continuum QCD using lattice simulations. We focus on the vicinity of the chiral crossover. We investigate the impact of finite volumes at zero...
Formulating bosonic field theories for quantum simulation is a subtle task. Ideally, one wants the smallest truncation of the bosonic Hilbert space that simultaneously exhibits a high degree of universality. But many of the most straight-forward truncations probably do not exhibit much universality. Meanwhile, recent work on the so-called "fuzzy" sigma model has shown promise as a very...
We present preliminary results of lattice QCD calculations for $D\pi$ scattering with isospin-$\frac{1}{2}$ and $\frac{3}{2}$. Using newly generated $N_f=2+1$ Wilson-Clover configurations by the CLQCD collaboration, we examine two volume extents ($L^3 \times T=32^3 \times 96$ and $48^3 \times 96$) at the same lattice spacing ($a=0.080$ fm) with a pion mass of $m_\pi \approx 290$ MeV. Employing...
Proton and neutron electric and magnetic form factors are the primary characteristics of their spatial structure and have been studied extensively over the past half-century. At large values of the momentum transfer $Q^2$ they should reveal transition from nonperturbative to perturbative QCD dynamics and effects of quark orbital angular momenta and diquark correlations. Currently, these form...
We apply Harris' ergodic theorem on Markov chains to prove
the geometric convergence of Hamiltonian Monte Carlo: first on compact
Riemannian manifolds, and secondly on a large class of non-compact Riemannian
manifolds by introducing an extra Metropolis step in the radial direction. We
shall use $\phi^4$ theory as an explicit example of the latter case.
We provide estimates for the light-quark-connected component of the RBC/UKQCD intermediate-window-hadronic contribution to the muon anomalous magnetic moment. We find significant tensions between our data-driven result,
$a_\mu^{W1,{\rmlqc}}=198.8(1.1)\times 10^{-10}$, and recent lattice computations.
The 't Hooft anomaly matching condition provides constraints on the phase structure at $\theta=\pi$ in 4D SU($N$) Yang-Mills theory. In particular, assuming that the CP symmetry is spontaneously broken at low temperature, it cannot be restored below the deconfining temperature at $\theta=\pi$. Here we investigate the CP restoration at $\theta=\pi$ in the 4D SU(2) case and provide numerical...
We report on the study of a version of the Riemannian Manifold HMC (RMHMC) algorithm, where the mass term is replaced by rational functions of the SU(3) gauge covariant Laplace operater.
RMHMC on a 2+1+1-flavor ensemble with near physical masses is compared against HMC, where increased rate of change in Wilson flow scales per fermion Molculardynamics step is observed.
We measure the static force directly by inserting chromo electric fields into the Wilson loop. We use the gradient flow to improve the signal-to-noise ratio, and to renormalize the field components. Furthermore, we can perform the continuum and zero flow time limit, obtaining a first direct determination of the QCD static force.
By comparing the lattice result with a perturbative calculation...
We present preliminary results for the $\rho(770)$ and $K^*(892)$ resonances using the Lüscher method. This work employs distillation on an RBC-UKQCD $N_f=2+1$ domain-wall fermion lattice with a physical pion mass. We consider irreducible representations with only leading $P-$wave contributions and extract the associated low-lying energy levels. These are used to parametrise the scattering...
The conventional discretisation of space-time entails a breaking of continuum symmetries and spoils the conservation of the associated Noether charges with ramifications for particle spectra and the renormalisation of central quantities, such as the Energy Momentum Tensor on the lattice.
In this work [1] we take first steps towards discretizing classical actions, while retaining its continuum...
When QCD is described by a non-relativistic EFT, operators consisting of gluonic correlators of two chromoelectric or -magnetic fields will often appear in descriptions of quarkonium physics. At zero T, these correlators give the masses of gluelumps and the moments of these correlators can be used to understand the inclusive P-wave decay of quarkonium. At finite T these correlators definite...
We compute the screening masses of fields with nucleon quantum numbers for a wide range of temperatures between $T \sim 1$ GeV and $T\sim 160$ GeV. The computation has been performed by means of Monte Carlo simulations of lattice QCD with $N_f=2+1$ flavors of $O(a)$-improved Wilson fermions: we exploit a novel strategy which has recently allowed to determine for the first time non-singlet...
Contour deformation methods have succesfully tamed sign problems in low-dimensional fermionic lattice fields theories at finite density. However, one obstacle with these methods is that they do not guarantee the existence of an integration contour which solves the sign problem completely, thus making it difficult for the methods to be applied to larger and more complex systems, such as lattice...
Deep Learning Models in the Machine Learning Community relies heavily on GPU-based tensor calculations. In recent years, Tensor Networks Methods have been explored to estimate the Partition Function of a system deterministically. One of the reasons Tensor Networks have not been yet utilised to the maximum potential in the Lattice Gauge Theories is their time complexity issue of the algorithms....
Significant tensions are observed between the dispersive and the lattice QCD results for hadronic vacuum polarization (HVP). We will present a general framework that allows to compare the two approaches and to combine them, if they can be reconciled. We have applied this framework to determine the distance or energy scales that could be responsible for the observed tensions and we will present...
In lattice-QCD calculations of parton distribution functions (PDFs) via large-momentum effective theory, the leading power (twist-three) correction appears as ${\cal O}(\Lambda_{\rm QCD}/P^z)$ due to the linear-divergent self-energy of Wilson line in quasi-PDF operators. For lattice data with hadron momentum $P^z$ of a few GeV, this correction is dominant in matching, as large as 30\% or more....
Euclidean Dynamical Triangulation as a lattice approach to quantum gravity has produced results that are compatible with semiclassical gravity in four dimensions. We explore the cosmological application of EDT by studying the behavior of the vacuum energy on the lattice. Although the lattice gravity calculations are broadly consistent with an emergent four-dimensional de Sitter space...
I will present a new method, developed in collaboration with M. Buzzicotti and N. Tantalo and based on deep learning techniques, to extract hadronic spectral densities from lattice correlators. Hadronic spectral densities play a crucial role in the study of the phenomenology of strong-interacting particles and the problem of their extraction from Euclidean lattice correlators has already been...
The sign problem has been an obstacle to first-principles calculations based on the Monte Carlo method. The Worldvolume Hybrid Monte Carlo (WV-HMC) method [Fukuma-Matsumoto 2020] is an efficient method to reduce the sign problem with low cost. In this talk, I apply the WV-HMC to the complex $\phi^4$ theory at finite density, and show that the computational cost is proportional to the degrees...
We establish that the charmed hadrons start dissociating at the chiral crossover temperature, $\mathrm{T_{pc}}$, leading to the appearance of charm degrees freedom carrying fractional baryon number. Our method is based on analyzing the second and fourth-order cumulants of charm ($\mathrm{C}$) fluctuations, and their correlations with baryon number ($\mathrm{B}$), electric charge ($\mathrm{Q}$)...
Euclidean Dynamical Triangulation (EDT) is a lattice approach to quantum gravity that has produced results compatible with semiclassical gravity in four dimensions. Although the lattice gravity calculations are broadly consistent with an emergent four-dimensional de Sitter space geometry, the calculations give corrections to a purely constant cosmological constant term. These corrections are...
The lattice gauge-scalar model with the scalar field in the fundamental representation of the gauge group has a single confinement-Higgs phase which is well-known as the Fradkin-Shenker-Osterwalder-Seiler analytic continuity theorem: Confinement and Higgs regions are subregions of an analytically continued single phase and there are no thermodynamics phase transitions between them.
In this...
We present the first ab-initio calculation of the $\pi^0$, $\eta$ and $\eta^{\prime}$ transition form factors at the physical point using lattice QCD with staggered fermions on $N_f = 2 + 1 + 1$ gauge ensembles, generated by the Budapest-Marseille-Wuppertal collaboration. We compare our results with existing measurements and with other theoretical estimates. Using these transition form...
We present our sparse modeling study to extract spectral functions from Euclidean-time correlation functions. In this study covariance between different Euclidean times of the correlation function is taken into account, which was not done in previous studies. In order to check applicability of the method, we firstly test it with mock data which imitate possible charmonium spectral functions....
We present recent updates on the lattice calculations of the valence-quark GPDs of the pion, the pion and kaon gluon PDF, and their first gluon moment in the physical-continuum limit. All these calculations are done on ensembles with $N_f = 2 + 1 + 1$ highly improved staggered quarks (HISQ), generated by the MILC Collaboration. The valence-quark GPD of the pion is done at lattice spacing...
The sign problem has been a major obstacle to first-principles calculations in various important physical systems. The Worldvolume Hybrid Monte Carlo (WV-HMC) method [Fukuma-Matsumoto 2020] may be a promising method towards solving the sign problem due to its versatility, reliability and low numerical cost. In this talk, I would like to report recent results on the application of the WV-HMC...
We investigate a possible relation between the chiral susceptibility and axial U(1) anomaly in lattice QCD at high temperatures. Employing the exactly chiral symmetric Dirac operator, we can separate the purely axial U(1) breaking effect in the connected and disconnected chiral susceptibilitesin a theoretically clean manner. Preliminary results for 2 and 2+1 flavor lattice QCD near the...
Distillation has been a useful tool in lattice spectroscopy calculations for more than a decade, enabling the efficient computation of hadron correlation functions. Nevertheless higher-dimensional compact operators such as baryons and tetraquarks pose a computational challenge as the time complexity of the Wick contractions grows exponentially in the number of quarks. This talk introduces a...
The Light-Cone Distribution Amplitude (DA) encodes the non-perturbative information of the leading Fock-component of the hadron wave function, therefore required for processes including exclusive hadron production. As the Pseudo-Nambu-Goldstone boson of QCD, nonperturbative structure of the pion is of particular interest. We present a lattice QCD calculation of the pion DA on ensembles with...
The lattice gauge-scalar model with the scalar field in the adjoint representation of the gauge group has two completely separated confinement and Higgs phases according to the preceding studies based on numerical simulations which have been performed in the specific gauge fixing based on the conventional understanding of the Brout-Englert-Higgs mechanism.
In this talk, we re-examine this...
We present our computation of the pion and eta-meson transition form factors from twisted mass lattice QCD at physical quark masses. In particular, we report on the improvements we recently made in the calculation of the pion transition form factor, which finalizes the calculation with data presently available to us. We use the form factors to determine the pseudoscalar-pole contributions to...
The Karsten-Wilczek action is a formulation of minimally doubled fermions on the lattice which explicitly breaks hypercubic symmetry and introduces three counterterms with respective bare parameters. We present a tuning of the bare parameters of the Karsten-Wilczek action on 4-stout configurations at the physical point.
We present results from simulations of a spin(4) lattice gauge theory in four
dimensions containing a single flavor of massless reduced staggered fermion. This model does not
allow for single site gauge invariant bilinear fermion terms and instead
we show that it develops a four fermion condensate in the confining regime. The absence of symmetry breaking is consistent with the cancellation...
In this talk, I summarize phenomenological results on topology, in particular the extraction of distinct topological sectors that resemble instantons, and support the picture of the QCD vacuum being filled with highly localized topological excitations.
Combining the identification of topological sectors (connected regions of either left- or right-handed winding in $n_f=2+1+1$ configurations)...
'Fit' independent methods are used to investigate temperature effects for the singly and doubly charmed spin $1/2$ baryons on the anisotropic FASTSUM 'Generation 2L' ensembles. Thereafter we determine where it is appropriate to apply standard fitting procedures in order to report the change in mass as the temperature increases. The negative parity sector is observed to be more strongly...
The light-cone distribution amplitude (LCDA) of the pion carries information about the parton momentum distribution and is an important theoretical input into various predictions of exclusive measurements at high energy, including the pion electromagnetic form factor. We provide constraints on the fourth Mellin moment of the LCDA using the heavy quark operator product expansion (HOPE) method.
In the conventional lattice formulation, conducting a Monte Carlo study of the Schwinger model (quantum electrodynamics in 1 + 1 dimensions) with a topological $\theta$ term or at finite density is almost impossible due to the sign problem. In this talk, I present the lattice formulation of the bosonized Schwinger model, which allows us to study the model using the Monte Carlo method without...
We present our implementation of the all-to-all meson field and low mode averaging (LMA) calculations, built on the Grid and Hadrons libraries. We discuss code optimizations made for staggered fermions and GPU offloading, as well as benchmark comparisons on leadership-class resources. We conclude with the statistical gains achieved using LMA for vector-current two-point functions relevant for...
The computation of the glueball spectrum is particularly challenging due to the rapid decay of the signal-to-noise ratio of the correlation functions. To address this issue, advanced techniques such as gauge link smearing and the variational method are commonly employed to identify the spectrum before the signal diminishes significantly. However, a significant improvement in the...
In this work we perform calculations in order to determine the renormalization factors and the mixing coefficients of the Yukawa and the quartic couplings in $\mathcal{N} = 1$ Supersymmetric QCD. The Yukawa couplings describe the interactions between gluino, quark and squark fields whereas the quartic couplings describe four-squark interactions. We discretize the action on a Euclidean lattice...
We present the status of the Mainz group's lattice QCD calculation of the transition form factor $\mathcal{F}_{\pi^0\gamma^\ast\gamma^\ast}$, which describes the interaction of an on-shell pion with two off-shell photons. This form factor is the main ingredient in the calculation of the pion-pole contribution to hadronic light-by-light scattering in the muon $g-2$,...
The problem of extracting spectral densities from Euclidean correlators
evaluated on the lattice has been receiving increasing attention.
Spectral densities provide a way to access quantities of crucial
importance in hadronic physics, such as inclusive decay rates,
scattering amplitudes, finite-volume energies, as well as transport
coefficients at finite temperature. Many approaches have...
Hadronic contributions dominate the uncertainty of the standard model prediction for the anomalous magnetic moment of the muon. In this talk, we will describe an ongoing lattice calculation of the hadronic, light-by-light, four-point function, performed with staggered fermions. The presence of quarks with different tastes complicates the analysis of this position-space correlation function. We...
Non-Abelian gauge fields having a line-singularity of the Dirac type lead us to violation of the non-Abelian Bianchi identity. The violation as an operator is equivalent to violation of Abelian-like Bianchi identities
corresponding to eight Abelian-like conserved magnetic monopole currents of the Dirac type in $SU(3)$ QCD. It is very interesting to study if these new Abelian-like monopoles...
The application of normalizing flows for sampling in lattice field theory has garnered considerable attention in recent years. Despite the growing community at the intersection of machine learning and lattice field theory, there is currently a lack of a software package that facilitates efficient software development for new ideas in this field. We present the idea of NeuLat, a fully...
In this talk, we will discuss a new method to calculate parton distribution functions (PDFs) from correlations of boosted quarks and gluons in the Coulomb gauge.
Compared to the widely used quasi-PDFs defined from gauge-invariant Wilson-line operators, such correlations offer advantages including absence of linear power divergence, enhanced long-range precision, and accessibility to larger...
We present our lattice simulations of gauge theories coupled to fermions and scalar fields in adjoint and fundamental representation. Supersymmetric gauge theories emerge as specific limiting cases within this theory space. We discuss our efforts to tune the parameters towards the supersymmetric limit.
Relativistic fermionic theories with four-Fermi interactions have a broad range of applications, e.g., as toy models for QCD as well as in condensed-matter physics. We study the simplest such theory, the so-called Gross-Neveu model, exposed to a background magnetic field in 2+1 dimensions. In the mean-field limit the model exhibits a rich phase structure when the magnetic field and the...
We review the level of welcomeness that members of the lattice field theory community feel based on the results of a survey performed in May and June 2023. While respondents reported generally high levels of feeling welcome at the lattice conference, women and people with diverse gender identities, sexual orientations, ethnic backgrounds and religious affiliations feel less included and have...
In this study we present lattice results on the QCD $\beta$-function in the presence of a quark mass. The $\beta$-function is calculated to three loops in perturbation theory and for improved lattice actions; it is extracted from the renormalization of the coupling constant $Z_g$. The background field method is used to compute $Z_g$, where it is simply related to the background gluon field...
We report basic properties of our new configuration set.We calculated the topological charge, the mass spectra for hadrons, and so on.The lattice spacing, $a^{-1}=2.339$[GeV], is fixed using the Omega baryon mass.
The ``Sphaleron Rate'' (imaginary linear-in-frequency part of the topological density retarded Green's function) determines the real-time relaxation rate of axial quark number for light quarks in a hot medium, and is relevant in heavy-ion collisions and electroweak baryogenesis. We recently showed how it can be determined in pure-glue QCD via standard Euclidean simulations, via a novel...
We report recent progress in data analysis on the two point correlation functions
which will be used to obtain form factors for the semileptonic decays $B_{(s)} \to D_{(s)}\ell\nu$.
We use a MILC HISQ ensemble ($a=0.12fm$ and $m_\pi = 310 MeV$) to produce the measurement data
using the HISQ light quarks and Oktay-Kronfeld (OK) action for the heavy quarks($N_f=2+1+1$ flavor).
We...
We present recent progress in evaluatinging $\varepsilon_K$, the indirect
CP violation parameter in the neutral kaon system, calculated using
lattice QCD inputs directly from the standard model.
We report recent progress on data analysis for 2-point correlation functions with HYP-smeared staggered quarks. We use the sequential Bayesian fitting method. We present how to obtain a good initial guess using the Newton method. We report results of fitting 2-point correlation functions, including the excited states, for $P \times P$ and $P \times A$ operators.
Workflow management has become an important topic in many research communities. Here, we focus on the particular aspect of provenance tracking. We follow the W3C PROV standard and formulate a provenance model for Lattice QCD that includes the ensemble-generation and the measurement parts of the Lattice QCD workflow. Since many important provenance questions in our community require extensions...
How and when do people become physicists? Are they always certain about their career choice? What are physicists like outside work? A team of physics students and faculty aim to answer these questions through the “My Journey as a Physicist” podcast. In each episode, a student host(s) interviews professional physicists to learn about their professional journey of how they ended up where they...
We examine the renormalized lattice spacing anisotropy in SU(2) Yang-Mills theory. We determine the physical anisotropy by performing anisotropic Wilson flow. Our preliminary findings indicate that, at high bare anisotropies, the physical anisotropy reaches a plateau. Further increase of the bare anisotropy results in a slight increase of the lattice spacings. Our findings can be then applied...
Here we present a lattice QCD determination of the first few Mellin moments of the pion distribution amplitude by analyzing the quasi-DA matrix elements using a lattice spacing of $a=0.836 \; \text{fm}$. Our work differs from previous work in that we use domain-wall fermions in order to respect chiral symmetry and that calculations are performed at the physical pion mass. First, we analyze...
The extraction of the QCD coupling via non-perturbative decoupling methods has been recently shown to be a compelling strategy for high-precision determinations [Eur. Phys. J. C 82 (2022) 12, 1092]. One of the key ingredients of this strategy is the determination of a (finite-volume) non-perturbative massive coupling at large values of the quark-mass, $M$. Robust continuum limit extrapolations...
Ab-initio calculations of real-time evolution for lattice gauge theory have very interesting potential applications but present challenging computational aspects.
We show that tensor renormalization group methods developed in the context of Euclidean-time lattice field theory can be applied to calculation of Trotterized evolution operators at real time. We discuss the optimization of...
General positivity constraints linking various powers of observables in energy eigenstates can be used to sharply locate acceptable regions for the energy eigenvalues, provided that efficient recursive methods are available to calculate the matrix elements. These recursive methods are derived by looking at the commutation relations of the observables with the Hamiltonian. We discuss how this...
The Pauli strings appearing in the decomposition of an operator can be can be grouped into commuting families, reducing the number of quantum circuits needed to measure the expectation value of the operator. We detail an algorithm to completely partition the full set of Pauli strings acting on any number of qubits into the minimal number of sets of commuting families, and we provide python...
Multilevel integration schemes are easy to couple with distillation, our current approach for computing highly optimized interpolating fields for hadrons. The locality of the distillation basis in the time direction can be exploited in accelerating the propagator computations with domain decomposition. Currently, we are exploring the use of asymmetric domain decomposition schemas in which the...
Numerous studies have demonstrated that the rapid decline in the efficiency of traditional sampling algorithms caused by Critical Slowing Down can be alleviated or even sidestepped completely using flow-based sampling. Such approaches trade off a reduction in autocorrelation times with an increase in the cost of generating new field configurations and an up-front training cost. The...
We present our ongoing work on the distribution amplitudes of the charmonia states $\eta_c(1s)$ and $J/\psi(1s)$. We use the so-called pseudo approach developed by A. Radyushkin in a set of three CLS $N_f=2$ ensembles at three different lattice spacings between $0.08~\text{fm}$ and $0.05~\text{fm}$ and a pion mass around $270~\text{MeV}$. The resulting momentum distributions can be studied in...
This work presents a study of Wuppertal smearing, comparing different mesons and kinematic configurations.
We propose a parametrization of the optimal smearing radius in terms of the reduced masses of the mesons, giving, at the same time, an estimate of the efficiency of the smearing in suppressing the excited states.
The relation between Momentum Smearing and ordinary Wuppertal smearing...
Hadronic scattering amplitudes determined in Lattice QCD using Lüscher’s formalism depend crucially on the finite-volume energy spectrum. This work presents some of the technical details of the determination of such spectra within the study of the two-poles nature of the $\Lambda(1405)$ from Lattice QCD. Starting with the extraction of energy states from correlation functions, the GEVP...
In this poster, I present preliminary results from the Fermilab Lattice and MILC collaborations on the nucleon axial charge and nucleon axial and vector form factors with the HISQ action for both valence and 2+1+1 sea quarks. For the nucleon axial charge, we compute correlators across four physical mass ensembles with approximate lattice spacings of 0.15, 0.12, 0.09, and 0.06 fm, and perform...
Normalizing flow based methods for sampling lattice gauge theories has shown some recent progress. Here, we present rudimentary results for observables with finite temperature on small lattices in 2+1 dimensions.
The phase diagram of QCD at finite density remains largely unknown due to the sign problem. We propose a 1+1 dimensional model which mimics some of the features of QCD in order to study how quantum computers can avoid the sign problem and allow computations at the finite density. The model is a Z(3) gauge theory coupled to 3 flavors of staggered fermions, and it features baryon-like...
We present results on three-particle scattering in the (1+1)-dimensional O(3) non-linear sigma model using lattice-determined finite-volume energies and the relativistic-field-theory (RFT) finite-volume formalism. We focus on the isospin-3 and isospin-2 three-particle channels, and perform lattice computations for four different volumes with three values of the lattice spacing each. The...
While Wick rotation to Euclidean spacetime is necessary for lattice QCD calculations, the subsequent rotation back to Minkowski spacetime from discrete correlator data is an ill-posed problem. In this proof-of-concept calculation, we compute correlation functions necessary for computing the hadronic tensor of the pion using existing ensembles generated by the MILC collaboration and $N_f=2+1+1$...
The Landau gauge four-gluon vertex is studied using high
statistical lattice simulations for several momentum configurations.
Furthermore, the outcome of the lattice QCD simulations are compared
with calculations performed with continuum Schwinger-Dyson equations.
Normalizing flow based methods for efficient sampling in lattice gauge theories have shown impressive progress. We have extended these methods to generate ensembles for SU(3) in 2+1 dimensions at a range of temporal extents. Preliminary results for observables are presented and future prospectives for finite temperature simulations are discussed
We present a new take on low-mode averaging, where the dimension of the low-mode subspace is multiplied by exploiting local coherence of low modes. The fraction of the quark propagator captured by this subspace can easily be volume averaged or sampled excessively and reaches gauge variance with lower computational cost than the traditional methods. The remainder piece can be sampled...
We present an evaluation of the glueball spectrum for configurations produced with $N_f=1$ dynamical fermions as a function of the $m_{\rm PCAC}$ mass. We obtained masses of states that fall into the irreducible representations of the octagonal group of rotations in combination with the quantum numbers of charge conjugation $C$ and parity $P$. Due to the low signal to noise ratio,...
In lattice QCD calculations, the trace of operator products involving the inverse Dirac operator is often necessary for evaluating various observables, such as cumulants of the chiral order parameter and conserved charge fluctuations. Since the Dirac operator is represented by a large sparse matrix on the lattice, the exact calculation of the trace is typically impractical. Instead, it is...
Two analysis techniques, the generalized eigenvalue method (GEM) or Prony's method (PM), are commonly used to analyze statistical estimates of correlation functions produced in lattice quantum field theory calculations. GEM takes full advantage of the matrix structure of correlation functions but only considers individual pairs of time separations when much more data exists. PM can be...
Python is a particularly appealing language to carry out data analysis, owing in part to its user-friendly character as well as its access to well maintained and powerful libraries like NumPy and SciPy. Still, for the purpose of analyzing data in a lattice QCD context, some desirable functionality is missing from these libraries. Moreover, scripting languages tend to be slower than compiled...
Common to many analysis pipelines in lattice field theory is the need to fit data to a model that is determined partially by a finite number of model parameters. Familiar examples include analyses of finite-size scaling and ground state spectroscopy. We propose a Bayesian fit method that utilizes a neural network to approximate the component of such models that is a priori unknown. The...
We use a regular tessellation of AdS$_2$ based on the (2,3,7) triangle group, with an extension to Euclidean AdS$_3$, to study the AdS/CFT correspondence. Perturbative calculations are verified and initial tests of monte carlo calculations for non-perturbative $𝜙^4$ theory exhibit critical phenomena on the boundary.
We report on a lattice fermion formulation with
a curved domain-wall mass term to nonperturbatively
describe fermions in a gravitational background.
In our previous work in 2022, we showed in the free
fermion theory on one and two-dimensional spherical domain-walls
that the spin connection is induced on the lattice
in a consistent way with continuum theory.
In this talk we add...
The density of any observable is equal to how large a volume there exist for each possible value of the observable. By considering the relative change to the volume along the direction of change of the observable, the relative change to the density of the observable can be obtained. I will show how one can calculate the change to the log of the density function rho and use this to calculate...
We present an update on our lattice calculations of the Mellin moments of PDFs and GPDs for the pion and kaon, using momentum-boosted meson states. In particular, we focus on the calculation of the scalar and tensor local operators, as well as the vector operator with up to three-covariant derivatives. The corresponding matrix elements allow us to extract the scalar and tensor charges, as well...
Macroscopic properties of the strong interaction near its chiral phase transition exhibit scaling behaviors, which are the same as those observed close to the magnetic transition in a 3-dimensional classical spin system with $O(4)$ symmetry. We show the universal scaling properties of the chiral phase transition in Quantum Chromodynamics (QCD) at the macroscale are, in fact, encoded within the...
Position-space schemes are very natural gauge-invariant non-perturbative renormalization schemes to implement on the lattice. The tradeoff is that the perturbative calculations required to convert to more typically used schemes such as MS are more theoretically involved. We present dimensionally regulated perturbative calculations of a set of HQET operators in position-space, allowing for...
The excited states contamination in the nucleon three-point function is one of the major systematic errors in calculating nucleon form factors. We use Bayesian Reconstruction to study the nucleon excited states in the two-point nucleon and S11 correlators which are constructed from the valence overlap fermions on DWF configurations at the physical pion mass with a lattice size of 5.5 fm. We...
Quadratic Unconstrained Binary Optimization (QUBO) problems can be addressed on quantum annealing systems. We reformulate the strong coupling lattice QCD dual representation as a QUBO matrix. We confirm that importance sampling is feasible on the D-Wave Advantage quantum annealer. We describe the setup of the system and present the first results obtained on a D-wave quantum annealer for U(N)...
Monte Carlo simulations with continuous auxiliary fields encounter challenges when dealing with fermionic systems due to the infinite variance problem observed in fermionic observables. This issue renders the estimation of observables unreliable, even with an infinite number of samples. In this talk, I will propose an approach to address this problem by employing a reweighting method that...
We present an update of the study of bag parameters of neutral $B_{(s)}$-meson mixing, which constrains the Standard Model as well as BSM scenarios. Our calculations use an all-domain-wall-fermion approach. We combine three lattice spacings ($1.7 \mathrm{GeV} \leq a^{-1} \leq 2.7 \mathrm{GeV}$) including 2 physical pion mass ensembles generated by RBC/UKQCD with ensembles with three finer...
We investigate the chiral transition of $U(N)$ lattice gauge theory based on the strong coupling expansion. A generalized vertex model with vertices and weights derived from the tensor network approach of the dual representation of lattice QCD with staggered fermions is used and the configurations are sampled by the Metropolis algorithm. We study the chiral transition in the chiral limit and...
The gravitational form factors (GFFs) of hadrons are related to the second Mellin moments of their generalized parton distributions. They can be extracted from matrix elements of the energy-momentum tensor of QCD. We present the gluon and quark flavor contributions to the GFFs of the pion and the nucleon in the kinematic region $0 \leq -t \leq 2~\text{GeV}^2$ on a clover improved ensemble with...
We present an analysis of the $N \pi$ contribution to the determination of the nucleon mass spectrum using constrained fits. Our study involves simultaneous fitting of $N \to N$ and $N \to N \pi$ correlation functions. The analysis is performed on a $24^3 \times 48 \times 24$ lattice with $2 + 1$ dynamical Domain-Wall fermions. We employ a lattice spacing of $a^{-1} = 1.74 \text{ GeV}$ and a...
Minimally doubled fermions realize one degenerate pair of Dirac fermions on the lattice. Similarities to staggered fermions exist, namely, spin and taste degrees of freedom become intertwined, and a remnant, non-singlet chiral symmetry and ultralocality are maintained. However, charge conjugation, isotropy and some space-time reflection symmetries are broken by the cutoff.
For two variants,...
We propose three independent methods to compute the hadron mass spectra of gauge theories in the Hamiltonian formalism. The determination of hadron masses is one of the key issues in QCD, which has been precisely calculated by the Monte Carlo method in the Lagrangian formalism. We confirm that the mass of hadrons can be calculated by examining correlation functions, the one-point function, or...
We present a novel approach to construct effective descriptions of a confining string. We consider a string pinned with heavy quark-antiquark endpoints on the lattice Yang-Mills theory (Kogut-Susskind Hamiltonian) as background with $SU(N_c)$ gauge symmetry with large $N_c$. Our approach describes the dynamics of the confining string as two different spin chains, which are both integrable. In...
We present first non-perturbative results for the renormalization constants of the QCD energy momentum tensor, based on the framework of thermal QCD with shifted and twisted (for quarks only) boundary conditions in the compact direction. We also show preliminary results for the entropy density obtained with the very same numerical strategy. This opens the way to the determination of the QCD...
We compute the low-lying spectrum of 4D SU(2) Yang-Mills in a finite volume using quantum simulations. In contrast to small-volume lattice truncations of the Hilbert space, we employ toroidal dimensional reduction to the ``femtouniverse" matrix quantum mechanics model. In this limit the theory is equivalent to the quantum mechanics of three interacting particles moving inside a 3-ball with...
Many applications in Lattice field theory require to determine the Taylor
series of observables with respect to action parameters. A primary example is
the determination of electromagnetic corrections to hadronic processes. We show
two possible solutions to this general problem, one based on reweigting, that
can be considered a generalization of the RM123 method. The other based on...
The trace of the energy momentum tensor (ETM) in the hadron gives the hadron mass. The trace anomaly due to the conformal symmetry breaking is believed to be an important ingredient for confinement. In this talk, I will show the trace anomaly form factors of the pion, nucleon and $\rho$ meson as functions of the squared momentum transfer $Q^2$ up to $\sim 4.3~\mathrm{GeV}^2$ which are...
Neutral meson mixing and meson lifetimes are theory-side parametrised in terms four-quark operators which can be determined by calculating weak decay matrix elements using lattice QCD.
While calculations of meson mixing matrix elements are standard, determinations of lifetimes typically suffer from complications in renormalisation procedures because dimension-6 four-quark operators can mix...
In a not well known paper [JHEP01(2008)076] it was shown how to perform interpolations between relativistic and static computations in order to obtain results for heavy-light observables for masses from (say) $m_{\rm charm}$ to $m_{\rm bottom}$. All quantities are first continuum extrapolated and then interpolated in $1/m=1/m_{\rm heavy}$. Large volume computations are combined with finite...
We study the various tensor renormalization group (TRG), such as the Higher-order TRG (HOTRG), Anisotropic TRG (ATRG), Triad TRG, and Tensor network renormalization (TNR) with the idea of projective truncation and truncated singularvalue decomposition (SVD) such as the randomized SVD (RSVD). The details of the cost function for the isometry determine the precision, stability, and calculation...
Laboratory setups and astrophysical circumstances may confine fermions to two spatial dimensions. Leading-order nonrelativistic pionless EFT in 2D has an anomalously broken conformal symmetry, and exhibits BKT phase transition. We use classic tools from lattice field theory to make predictions about this strongly correlated system.
We express non-linear sigma O(3) model in a form suited to continuous variable (CV) approach to quantum computing by rewriting the model in terms of boson operators in an infinite-dimensional Hilbert space. We show that it is possible to reach the scaling regime with truncation of the Fock space by considering $\mathcal{O}(10)$ photons at each site. This is an indication that it might be...
Non-orthogonal background electromagnetic fields generate a non-zero expectation value for the topological charge in QCD. For sufficiently weak fields, a linear response is expected. This linear response has been studied and related to the QCD contribution to the axion-photon coupling, for which we give preliminary results at finite lattice spacing. We also investigated the dependence of the...
Quark orbital angular momentum in the proton is evaluated via a Lattice QCD calculation of the second Mellin moment of the twist-3 generalized parton distribution $\widetilde{E}_{2T} $ in the forward limit. The connection between this approach to quark orbital angular momentum and approaches previously utilized in Lattice QCD calculations, via generalized transverse momentum-dependent parton...
Neutrino oscillation experiments require accurate reconstructions of neutrino energies, which depend in part on a theoretical understanding of the axial $N \rightarrow \Delta$ transition form factors. A lattice QCD study of this transition will require construction of all hadronic states with energies up to $m_\Delta$, which at the physical point includes $N\pi$ and $N\pi\pi$. Building...
We present preliminary results for B-physics from a combination of non-perturbative results in the static limit with relativistic computations satisfying $am_{\rm heavy}<<1$. Relativistic computations are carried out at the physical b-quark mass using the Schrödinger Functional in a $(0.5~{\rm fm})^4$ box. They are connected to large volume observables through step scaling functions that trace...
Machine learning, deep learning, has been accelerating computational physics, which has been used to simulate systems on a lattice. Equivariance is essential to simulate a physical system because it imposes a strong induction bias for the probability distribution described by a machine learning model. However, imposing symmetry on the model sometimes occur a poor acceptance rate in...
We present the first lattice QCD results of the second order fluctuations of and correlations among net baryon number, electric charge and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field with physical pion mass $m_\pi$ = 135 MeV. To mimic the magnetic field strength produced in the early stage of heavy-ion collision experiments we use 6 different values...
Gapped fermion theories with gapless boundary fermions can exist in any number of dimensions.
When the boundary has even space-time dimensions and hosts chiral fermions, a quantum Hall current
flows from the bulk to the boundary in a background electric field. This current compensate for the
boundary chiral anomaly. Such a current inflow picture is absent when the boundary theory is...
Studies of the $\Delta$ baryon resonance and the $K_0^\ast(700)$ and $a_0(980)$ meson resonances using $N_f=2+1$ lattice QCD for pion masses near 200 MeV are presented. The role of tetraquark operators in the mesonic systems is detailed. The $s$-wave scattering lengths for both the $I=1/2$ $N \pi$ and $I=3/2$ $N \pi$ channels and properties of the $\Delta$ resonance are identified from the...
We review recent suggestions to quantum simulate scalar electrodynamics (the lattice Abelian Higgs model) in 1+1 dimensions with rectangular arrays of Rydberg atoms. We show that platforms made publicly available recently allow empirical explorations of the critical behavior of quantum simulators. We discuss recent progress regarding the phase diagram of two-leg ladders, effective Hamiltonian...
In this review, I will cover the status of the calculations of quantities that are needed in the analysis of neutrinos off nuclear targets. These include the axial charge and the form factors of the nucleon. A discussion of systematics—removing excited state contributions and obtaining results at the physical point will be included. Looking ahead, I will conclude with prospects of...
We discuss the applicability of lattice QCD to the long-distance (LD) two-photon contribution to the decay of a long-lived neutral kaon into a charged-muon pair (KL2mu). In the absence of QED, the flavor-changing neutral-current KL2mu process requires exchanging at least two W-bosons or a W- and a Z-boson, the short-distance (SD) contribution. Such a process is suppressed by two factors of...
Recently, significant progress has been made in improving the efficiency and computational speed of lattice QCD calculations associated with Generalized Parton Distributions (GPDs). These advancements are a result of employing asymmetric frames, which differ from the commonly used symmetric frames, and introducing flexibility in the distribution of transferred momentum. A key element of our...
We present the first continuum extrapolated results for the chiral magnetic effect (CME) and the chiral separation effect (CSE) conductivities in equilibrium with staggered fermions at physical masses. We simulate QCD in a constant magnetic background and measure respective chemical potential derivatives of the currents appearing in each effect. The conductivities are calculated as a function...
This talk will discuss a method for computing the energy spectra of quantum field theory utilizing digital quantum simulation. A quantum algorithm called coherent imaging spectroscopy quenches the vacuum with a time-oscillating perturbation and reads off the excited energy levels from the loss in the vacuum-to-vacuum probability following the quench. As a demonstration, we apply this algorithm...
The Lüscher formalism is a well-known and widely used method for extracting scattering amplitudes from the finite-volume spectrum. Recent lattice QCD calculations involving systems where a lighter particle couples to heavier scattering particles (e.g. baryon-baryon scattering) have highlighted the limitations of the standard formalism below threshold. This is due to the presence of left-hand...
We present a method for analytic continuation of Euclidean Green functions computed using lattice QCD. The method is based on conformal maps and construction of an interpolation function which is analytic in the upper half plane. A novel aspect of our method is rigorous bounding of systematic uncertainties, which are handled by constructing the full space of interpolating functions (at each...
The so-called trivializing flows were proposed to speed up Hybrid Monte Carlo
simulations, where the Wilson flow was used as an approximation of a
trivializing map, a transformation of the gauge fields which trivializes the
theory. It was shown that the scaling of the computational costs towards the
continuum did not change with respect to HMC. The introduction of machine
learning...
In this talk, I will focus on naturalness considerations in SM/2HDM augmented by a Triplet field, here dubbed as Higgs Triplet Models. I will show that the Veltman conditions in HTM are modified by virtue of the additional scalar charged states and that one loop quadratic divergencies can be driven to zero within the allowed respective parameter spaces, usually constrained by unitarity and...
The complex Langevin method shows great promise in enabling the calculation of observables for theories with complex actions. Nevertheless, real-time quantum field theories have remained largely unsolved due to the particular severity of the sign problem. In this contribution, we will discuss our recent progress in applying the complex Langevin method to SU(2) Yang-Mills theory in 3+1...
Understanding three-body dynamics is crucial in comprehending the behavior of hadronic states that decay into three or more particles under strong interactions. Recent advances in Lattice QCD techniques allow us to calculate three-particle interactions from QCD and access finite volume energies. Connecting these energies to physical observables involves multiple steps. Firstly, we use the...
Dilepton decays of the pseudoscalar mesons have been drawing particular interest, thanks to their sensitivity to both the QCD dynamics at low energy and also signals beyond the Standard model. In the first part of the talk, we present our work on an improved Standard-Model prediction for the rare decay $\pi^0 \to e^+e^-$, and compare it with the first determination on the lattice that...
First lattice QCD calculations of x-dependent GPD have been performed in the Breit frame, where the momentum transfer is evenly divided between the initial and final hadron states. Employing the asymmetric frame proposed in PRD 106 (2022) 11, 114512, we are able to obtain proton GPDs for multiple momentum transfers in a computationally efficient setup. In this presentation, we focus on the...
We present an analysis of newly expanded and refined data from lattice studies of the SU(3) gauge theory with $N_f=8$ light Dirac fermions, a theory which lies close to the boundary of the conformal window. We first assume that this theory is just outside the conformal window and identify a light unflavored scalar meson in this case as an approximate dilaton. We show fits of the lattice data...
The minimal renormalon subtraction introduced by Komijani and used by the Fermilab Lattice, MILC, and TUMQCD Collaborations to determine quark masses is extend to other quantities. A simpler derivation of the renormalon normalization is presented, showing at the same time how it is completely general. The scale dependence of the Borel sum is investigated.
Quantum simulations of lattice gauge theories are currently limited by the noisiness of the physical
hardware. Various error mitigation strategies exist to extend the use of quantum computers. We perform quantum simulations to compute two-point correlation functions of the 1 + 1d Z2 gauge theory with matter to determine the mass gap for this theory. These simulations are used as a laboratory...
The 2D O(3) model has been widely used as a toy model for quantum chromodynamics and ferromagnetism. It shares fundamental features with quantum chromodynamics, such as being asymptotically free. It is possible to define a trivializing map, a field transformation from a given theory to trivial variables, through a gradient flow. An analytic solution to this trivializing flow may be obtained by...
While approximations of trivializing field transformations for lattice path integrals were considered already by early practitioners, more recent efforts aimed at ergodicity restoration and thermodynamic integration formulate trivialization as a variational generative modeling problem. This enables the application of modern machine learning algorithms for optimization over expressive...
We have studied the chiral and confinement-screening phase transitions in the Schwinger model at finite temperature and density using the quantum algorithm.
The theoretical exploration of the phase diagram for strongly interacting systems at finite temperature and density remains incomplete mainly due to the sign problem in the conventional Lattice Monte Carlo method.
However, quantum...
Rare decays of charged and neutral Kaons will be discussed. Phenomenological works being done in collaboration with Enrico Lunghi and another one with Stefan Schacht will be discussed. Mode(s) that should be target for precision lattice study...
The recently discovered I = 0, JP = 1+ doubly-charmed tetraquark Tcc(3875) is an exotic meson that is a candidate for a DD molecule. In nature, it decays to DDπ, since the D is unstable. It has been studied on the lattice for heavier-than-physical quark masses for which the D* is stable, so that two-particle methods can be used. However, a major drawback of this methodology is that the...
We compute the sphaleron rate on the lattice. We adopt a novel strategy based on the extraction of the spectral density via a modified version of the Backus-Gilbert method from finite-lattice-spacing and finite-smoothing-radius Euclidean topological charge density correlators. The physical sphaleron rate is computed by performing controlled continuum limit and zero-smoothing extrapolations.
Beyond spectral quantities, Symanzik Effective Theory (SymEFT) predictions of the asymptotic lattice-spacing dependence require the inclusion of an additional minimal basis of higher-dimensional operators for each local field involved in the matrix element of interest. Adding the proper bases for fermion bilinears of mass-dimension 3 allows to generalise previous predictions to matrix elements...
The mesonic $f_{PS} / m_V$ and $f_V / m_V$ ratios, with f the decay constant and m the meson mass, are calculated in mass perturbed conformal gauge theories to NNLO and N$^3$LO orders, respectively. Here NNLO and N$^3$LO refer to the non-relativistic effective theory expansion which is the applicable framework. The results are expanded a la Banks-Zaks in order to end up with scheme-independent...
Generalized parton distribution functions (GPDs) describe the longitudinal momentum distribution within a hadron among its constituent partons as well as information about the momentum in the transverse direction. We calculate unpolarized and helicity GPDs using 2+1+1 flavors of highly improved staggered quarks in ensembles generated by the MILC collaboration at a=0.09 fm with a physical pion...
Stochastic locality, arising from the mass gap of QCD, allows for independent fluctuations in distant regions of lattice gauge field configurations.
This can be used to increase statistics and, in the extreme case of the master-field approach, obtain an error estimate from a single configuration.
However, spatially-separated samples at moderate distances show residual correlation that needs...
We construct neural networks that work for any Lie group and maintain gauge covariance, allowing smooth and invertible transformations of gauge fields. We implement the transformations for 4D SU(3) lattice gauge fields, and explore their use in HMC. Our current research develops various loss functions and optimizes field transformation accordingly. We show the effect of these transformations...
We report our recent results for $K\to\pi\pi$ matrix elements and $\varepsilon'$, the measure of direct CP violation, released on arXiv:2306.06781. This is RBC/UKQCD's first result for $\varepsilon'$ with periodic boundary conditions (PBC), while our earlier calculations were performed with G-parity boundary conditions, where the isospin-0 two-pion ground state corresponds to the on-shell...
The LSD collaboration is studying Stealth Dark Matter, an SU(4) gauge theory, whose ground state spin-0 baryon is the dark matter candidate. We are investigating Stealth Dark Matter with two fermions in the fundamental representation using the quenched approximation. I will discuss our baryon operator construction using LapH and lattice octahedral group irreps. Then I will present the latest...
The thermal photon emissivity at the QCD chiral crossover is
investigated using imaginary momentum correlators. These have been
measured on a newly generated $20 \times 96^3$ lattice-QCD ensemble
with $\mathrm{O}(a)$-improved Wilson quarks and physical up, down and
strange quark masses at a temperature $T=154$ MeV near the
pseudo-critical temperature. In order to realize the photon...
The K-matrix parametrizes short-range interactions in the relativistic-field-theory finite-volume formalism. It is related to the infinite-volume scattering amplitude, thus providing a bridge between the lattice and perturbation theory, as well as a handle on finite-volume effects and the pion mass dependence. However, leading-order perturbative calculations agree very poorly with the results...
Generalized Parton Distributions (GPDs) are related to one aspect of nucleon tomography, the 3D imagining the proton. In one limit, the GPD can describe both the longitudinal momentum and the transverse position of a parton. In other limits, the GPD can describe how each parton contributes to the total spin or mass of the nucleon. Nucleon tomography has sparked great interest as a goal of many...
An effective way to design quantum algorithms is by heuristics. One of the representatives is Farhi et al.’s quantum approximate optimization algorithm (QAOA), which provides a powerful variational ansatz for ground state preparation. QAOA is inspired by the adiabatic evolution of a quantum system, and the ansatz can encode the real time evolution of the system Hamiltonian. In this work, we...
Many hadronic resonances, including the most intriguing ones (Roper, $\pi_1$(1600), or $T^+_{cc}$(3872)), decay into three or more particles. In principle, one can determine their properties from the multi-body version of the Luscher finite-volume scattering formalism. However, one of the obstacles in specifying their masses from Lattice QCD is the lack of developed three-body amplitude...
I will highlight existing limitations of the current architecture of Normalizing flows as applied to the generation of lqcd samples. From the Geometric Deep Learning perspective, existing architecture utilized the most basic features - invariant quantities that correspond to isotropic filters. In order to establish an expressive flow model transforming base distribution to target, I will...
Several SU(N) gauge theories have been explored as candidates for producing stable dark matter particles that can explain their relative abundance, while also evading current constraints from direct, indirect and collider searches. In this talk, I will present the confinement and spectral properties of a new model we name Hyper Stealth Dark Matter, which involves an SU(4) gauge theory with 1...
Lattice studies of spontaneous supersymmetry breaking suffer from a sign problem that in principle can be evaded through novel methods enabled by quantum computing. I will present ongoing work exploring ways quantum computing could be used to study spontaneous supersymmetry breaking in lower-dimensional lattice systems including the (1+1)d N=1 Wess--Zumino model. A particularly promising...
Using numerical lattice simulations, we analyze the influence of uniform rotation on the equation of state of gluodynamics. For a sufficiently slow rotation, the free energy of the system can be expanded into a series of powers of angular velocity. We calculate the moment of inertia given by the quadratic coefficient of this expansion and determine its dependence on the temperature We find...
We present a proposal for calculating the running of the coupling constant of the $SU(3)$ pure gauge theory, which combines the Twisted Gradient Flow (TGF) renormalization scheme with Parallel Tempering on Boundary Conditions (PTBC). The TGF is a gradient flow-based renormalization scheme formulated in an asymmetric lattice with twisted boundary conditions. Combined with step scaling, it has...
We present progress towards extracting multi-hadron $D$ decay amplitudes, such as $D \to \pi \pi$, in a pilot study using three ensembles of stabilised Wilson fermions at the SU(3) flavour symmetric point, with $M_\pi = 410$ MeV. As the three ensembles differ only in the lattice spacing, with well matched physical volumes, it is possible to perform a continuum limit for finite-volume energies...
Understanding the intricate three-dimensional internal structure of the nucleon has been a long-standing challenge. The main quantitative tool to map this structure are the generalized parton distributions (GPDs). In this talk, we present the first extraction of unpolarized GPDs using the pseudo-distribution approach on the lattice. We use one ensemble of $N_f=2+1+1$ twisted mass fermions at a...
We are examining one-flavour $SU(N_c)$ gauge theories with one fermion in the antisymmetric representation as a candidate to approximate $\mathcal{N}=1 $ SYM due to their equivalence in the large-$N_c$ limit. Summarising results on spectral evaluations of $N_c=3$, we will report on the progress of dynamical calculations for $N_c > 3$. Here we will discuss cutoff effects and challenges in...
In this talk we introduce a novel quantum algorithm for the estimation of thermal averages
in the NISQ-era through an iterative combination of Variational Quantum Eigensolver techniques and reweighting.
We discuss the details of the algorithm and the scaling of resources and systematical errors,
showing some results of the application to compelling test cases.
Normalizing flows are machine-learned maps between different lattice theories which can be used as components in exact sampling and inference schemes. Ongoing work yields increasingly expressive flows on gauge fields, but it remains an open question how flows can improve lattice QCD at state-of-the-art scales. This talk discusses and demonstrates several useful applications which are viable...
The rare hyperon decay $\Sigma \to p \ell^+ \ell^-$ is a flavour changing neutral current process that is sensitive to new physics beyond the Standard Model.
We present the current status of the first exploratory calculation of this decay on the lattice with 340 MeV pions using domain wall fermions.
We generalize the relativistic field-theoretic (RFT) three-particle finite-volume formalism to systems of three identical, massive, spin-$1/2$ fermions, such as three neutrons. This allows, in principle, for the determination of the three-neutron interaction from the finite-volume spectrum of three-neutron states, which can be obtained from lattice QCD calculations.
Triviality of phi4 theory in four dimensions can be avoided if the bare coupling constant is negative in the UV. Theories with negative coupling can be put on the lattice if the integration domain for phi(x) is contour-deformed from the real to the complex domain. In 0+1d (quantum mechanics), one can recover results from PT-symmetric quantum mechanics in this way. In this talk, I report on an...
We present the first lattice calculation of the four twist-3 axial quark GPDs for the proton in the $N_f=2+1+1$ twisted-mass formulation with a clover improvement. The ensemble has a volume $32^3\times64$, lattice spacing 0.0934 fm, and corresponds to a pion mass of 260 MeV. The calculation used the quasi-GPDs approach, which requires matrix elements with momentum-boosted proton states coupled...
Novel regularizations of lattice gauge theories can potentially enable faster classical or quantum simulation, but the landscape of available regularizations and their continuum limits is not fully understood. Our recent work adds a point to this landscape by introducing a generalization of U(1) lattice gauge theory obtained by applying a boundary condition in group space with a twist angle...
Quantum computation often suffers from artificial symmetry breaking. We should strive to suppress the artifact both by theoretical and technical improvements. As for chiral symmetry, there is a celebrated theoretical formalism, i.e., the overlap fermion. In this presentation, I will talk about how the overlap fermion guarantees chiral symmetry in quantum computation. I will also show that,...
We present results for O(1/m) and O(1/m^2) relativistic corrections to the static potential. The potentials are computed using Wilson loops with two colour-field insertions. To renormalize the inserted fields, we applied Gradient flow to the correlator. This also leads to a significant improvement of the signal-to-noise ratio, providing access to loops with large spatial and temporal extent.
The TMD soft function may be obtained by formulating the Wilson line in terms of auxiliary 1-dimensional fermion fields on the lattice. In the "timelike" region, this corresponds to the moving heavy quark effective theory (HQET). I present the results of the one-loop calculation of the Euclidean space analog to the soft function, and show that it must proceed in the "spacelike" region....
We update our previous results and also determine $F_K$ and $F_\pi$ separately using Möbius domain-wall fermions computed on gradient-flowed $N_f$ = 2 + 1 + 1 highly-improved staggered sea-quark ensembles. We use five values of the pion mass ranging from 130 $\le$ $m_\pi$ $\le$ 400 MeV, four lattice spacings of a $\sim$ 0.15, 0.12, 0.09, 0.06 fm and multiple lattice volumes. The physical...
We apply constant imaginary offsets to the path integral for a reduction of the sign problem in the Hubbard model. These straightforward transformations enhance the quality of results from HMC calculations without compromising the speed of the algorithm. This method enables us to efficiently calculate systems that are otherwise inaccessible due to a severe sign problem. To support this claim,...
The scientific method is underpinned by reproducibility, however, parallel computing often violates this through lack of associativity when summing floating point numbers. For Lattice QCD calculations this can have several undesirable effects, such as dramatic variations in solver iteration count, as well as the fundamental inability to exactly reproduce a given Monte-Carlo generated...
In this work we consider strongly interacting dark matter candidates which are composite states of $N_f=2$ fermions charged under a Sp(4) gauge group in the fundamental representation. We present first results from lattice calculations for the scattering properties of two pseudo-Goldstone bosons in the isospin I=2 channel. We report results for searches for bound states and resonances and...
We determine the value of $|V_{us}|$ using the kaon semileptonic form
factor calculated from the PACS10 configurations, whose physical
volumes are more than (10 fm)$^4$ at the physical point. The configurations
were generated using the Iwasaki gauge action and $N_f=2+1$ stout-smeared
nonperturbatively $O(a)$ improved Wilson quark action at the three lattice
spacings, 0.085, 0.063, and...
We present results for the potential of two static anti-quarks in the presence of two light quarks. We improve on existing results the $\bar b \bar b u d$ tetraquark system by computing the static potential at off-axis separations, significantly increasing the number of data points in the crucial region of small distances. Moreover, we show entirely new results for the static potential of a...
This work presents a determination of the quark Collins-Soper kernel, which relates transverse-momentum-dependent parton distributions (TMDs) at different rapidity scales, using lattice quantum chromodynamics (QCD). This is the first lattice QCD calculation of the kernel at quark masses corresponding to a close-to-physical value of the pion mass, with next-to-next-leading logarithmic matching...
The numerical sign problem poses a seemingly insurmountable barrier to the simulation of many fascinating systems.
We apply a neural networks to deform the region of integration, mitigating the sign problem of systems with strongly correlated electrons.
In this talk we present our latest architectural developments as applied to contour deformation.
We also demonstrate its applicability...
In the current climate and energy crisis context, it is crucial to study and optimise the energy efficiency of scientific software used at large scale computing facilities. This supports moving toward net-zero computing targets, and reduce the negative impact of growing operational costs on the production of scientific data.
The energy efficiency of a computation is generally quantified as an...
Constructing improved Hamiltonians for gauge theories coupled to fermionic matter will be important for improving continuum limit extrapolations of quantum computations. In this talk we will present a formulation for simulating ASQTAD fermions for lattice computation and provide fault tolerant resource costs in terms of primitive operations. We additionally show tha tthe scaling of energies...
We study the three dimensional principal chiral model using both the triad tensor renormalization group method, and the anisotropic tensor renormalization group method. We present a tensor network formulation for the model, and compare the ability of the two methods to measure thermodynamic observables. In addition we remark upon criticality, and the possible universality class of the phase...
First order phase transitions in the early universe might produce a detectable background of gravitational waves. As these phase transitions can be generated by new physical sectors, it is important to quantify these effects. Many non-Abelian pure Yang-Mills gauge theories are known to have first order deconfinement phase transitions, with properties that can be studied with lattice...
Bond-weighted tensor renormalization group (BTRG) is a novel tensor network algorithm to improve the accuracy in calculating the partition functions of the classical spin models. We extend the BTRG to make it applicable for the fermionic system, benchmarking with the two-dimensional massless Wilson fermion. We show that the accuracy with the fixed bond dimension is improved also in the...
In the context of Composite Higgs Models, where the standard model Higgs is interpreted as a pseudo Nambu–Goldstone Boson, baryons formed by matter in different representations, known as chimera baryons, could serve as top partners. The chimera baryon sharing the same quantum number as the top quark can mix with it, effectively lifting the mass of the top quark through the see-saw mechanism....
Quantum hardware in the NISQ era suffers from noise, which affects the reliability and accuracy of quantum computation. Here we present a comparison of quantum error mitigation strategies for Hamiltonian simulation and variational quantum algorithms, using as test bench some simple quantum fermionic systems and discrete gauge theories.
We present a method for computing hybrid static quark-antiquark potentials in lattice QCD based on Laplace trial states. They are formed by eigenvector components of the covariant lattice Laplace operator and their covariant derivatives. The new method does not need complicated gauge link paths between the static quarks and makes off-axis separations easily accessible. We show first results...
Inclusive hadronic $\tau$ decays are very interesting from the phenomenological viewpoint since they give access to the CKM matrix elements $V_{ud}$ and $V_{us}$. In this talk, exploiting flavour diagonal vector and axial two-point correlators produced with high statistics by ETMC within the muon $g-2$ HVP project, we apply the HLT method for hadronic smeared spectral densities to study the...
We present one-loop perturbative results of the renormalization functions for a complete set of nonlocal quark bilinear operators containing an asymmetric staple-shaped Wilson line, using a family of improved lattice actions. This study is relevant for the nonperturbative investigations regarding the renormalization of the unpolarized, helicity and transversity transverse-momentum dependent...
We study the entanglement entropy in SU(3) pure gauge theory due to the presence of static quarks. Using a replica approach we investigate the q=2 Renyi entropy across various partitions of space A and \bar{A}. We use this to find the excess entanglement entropy induced by the presence of a quark pair in confinement, and by the presence of a single quark in deconfinement. At 4/3 Tc, we find...
We report on how adjoint zero modes can be used to filter out the topological structures of gauge configurations from the UV fluctuations. The techniques presented here look promising to investigate regimes relevant to recent studies based on semiclassical methods. A particularly interesting application is to test whether the dynamics of fractional instantons can explain properties of the...
In the quantum simulation of lattice gauge theories, gauge symmetry can be either fixed or encoded as a redundancy of the digitized Hilbert space. While fixing the gauge saves the number of qubits to digitize the Hilbert space, keeping the gauge redundancy can provide space to mitigate and correct certain quantum errors by checking and restoring Gauss's law. In this talk, we treat the gauge...
Direct simulations of real-time dynamics of strongly correlated quantum fields are affected by the NP-hard sign sign-problem, which requires system-specific solution strategies [1].
Here we present novel results on the real-time dynamics of scalar field theory in 1+1d based on our recently developed machine-learning assisted kernelled complex Langevin approach [2]. By using simple field...
Four-dimensional gauge theories based on symplectic Lie groups have been introduced as the microscopic origin for elegant proposals of several new physics models. Numerical studies pursued on the lattice can provide the quantitative information necessary for the application of such models.
To this purpose, we implemented $Sp(2N)$ gauge theories using Monte Carlo techniques within Grid, a...
We present a study of the 3D O(2) non-linear $\sigma$-model on the lattice, which manifests topological defects in the form of vortices. They tend to organize into vortex lines that bear strong analogies with global cosmic strings. Therefore, this model serves as a testbed for studying topological defects. Moreover, the model undergoes a second-order phase transition, hence it is appropriate...
The nucleon-hyperon interaction is important to understand the system with strange quarks, for example, the inner region of neutron stars. Although experimental study of the interaction is difficult rather than the nucleon-nucleon interaction, which is so-called nuclear force, theoretical study is possible by using the HAL QCD method in the lattice QCD. In the present contribution, we show our...
We report on first computations of hadron masses and matrix elements with
charm quarks in O$(a)$ improved (2+1)-flavour lattice QCD in the framework of
stabilised Wilson Fermions.
Employing SU(3)-flavour-symmetric gauge field ensembles from the OpenLAT initiative, we study two strategies how to fix the physical charm quark mass.
In a first approach, we follow the standard procedure by...
Composite Higgs models are a class of models proposed to address the hierarchy and naturalness problems associated with the Standard Model fundamental scalar Higgs. $SU(2)$ with two fundamental flavours is a minimal model for the composite Higgs sector which is not yet ruled out by experimental data. We present lattice results for $SU(2)$ with two fundamental mass degenerate flavours. For the...
We compute the Kugo-Ojima function $u(q^2)$ using large lattice
volume simulations, study the volume dependence, and compare with
analytical results from Schwinger-Dyson equations. Special attention is
given to the infrared behaviour of $u(q^2)$ and the connection with
confinement criteria.
We simulate lattice QED in (strong) external electromagnetic fields using techniques developed for simulating lattice QCD. We are currently simulating lattice QED in constant external magnetic fields to observe the chiral symmetry breaking predicted by Schwinger-Dyson studies. Difficulties in extending these studies to include external electric fields are discussed.
Ab-initio Monte Carlo simulations of strongly-interacting fermionic systems are plagued by the fermion sign problem, making the non-perturbative study of many interesting regimes of dense quantum matter, or of theories of odd numbers of fermion flavors, challenging. Moreover, typical fermion algorithms require the computation (or sampling) of the fermion determinant. We focus instead on the...
We explore relations between quantum error correction and gauge theory. They have a conceptual similarity that quantum error correction provides a redundant description of logical qubits in terms of encoded qubits while gauge theory has a redundancy to describe physical states. Motivated by the conceptual similarity and recent demand for efficient ways to put gauge theories on quantum...
In this study, we investigate renormalization of gauge-invariant nonlocal gluon operators up to one-loop in lattice perturbation theory. Our computations have been performed in both Dimensional and lattice regularizations, using the Symanzik improved gluon action, leading to the renormalization functions in the modified Minimal Subtraction $(\overline{MS})$ scheme, as well as conversion...
In the region of hard photon energies, radiative leptonic decays represent important probes of the internal structure of hadrons. Moreover, radiative decays can provide independent determinations of Cabibbo-Kobayashi-Maskawa matrix elements with respect to purely leptonic or semileptonic channels. Prospects for a precise determination of leptonic decay rates with emission of a hard photon are...
I discuss our progress in studying the two-nucleon spectrum at heavy pion mass using various types of interpolating operators to create the correlation functions. These include momentum-space creation and annihilation operators using the stochastic Laplacian Heaviside method both with and without local hexa-quark interpolators, local hexa-quark creation operators and momentum space...
We study effects of gauge smearing on the nucleon and meson gluon-PDF matrix elements, considering hypercubic smearing, stout smearing, and Wilson flow. The lattice calculations are carried out with $N_f = 2 + 1 + 1$ highly improved staggered quarks in ensembles generated by the MILC Collaboration. We use clover fermions for the valence action on one lattice spacing $a \approx 0.12$ fm and...
In this investigation we study the most general two Higgs doublet model with
SU(2) gauge fields on the lattice.
The phase space is probed through the computation of gauge-invariant global
observables serving as proxies for order parameters.
In each phase, the spectrum of the theory is analysed for different combinations
of bare couplings and different symmetry breaking patterns.
The...
State-of-the-art algorithms for simulating fermions coupled to gauge fields often rely on integrating fermion degrees of freedom. While successful in simulating QCD at zero chemical potential, at finite density these approaches are hindered by the sign problem, for example, leading to extensive research on alternative formulations suitable, inter alia, for simulations of gauge theories on...
We compute non perturbatively the RG running of the complete basis of $\Delta F=2$ four fermion operators in the chirally rotated Schrödinger Functional in the region of energies between the $W$ mass and the switching scale (4GeV).
The possibility to use fault-tolerant Quantum Computers in the "Beyond the NISQ era" is a promising perspective: it could bring the implementation of Markov Chain Monte Carlo (MCMC) quantum algorithms on real machines. Then, it would be possible to exploit the quantum properties of such devices to study the thermodynamic properties of the system. This also allows us to avoid the infamous sign...
I will present updated results from the NPLQCD collaboration including a variational study of $NN$ systems at $m_\pi\sim800$MeV on two lattice volumes, using a set of interpolating operators that includes non-local products of plane-wave baryons as well as operators spanning the full Hilbert space of local six-quark operators. I will also show a first glance at the results of the same analysis...
The Witten effect predicts that a magnetic monopole acquires a fractional electric charge inside topological insulators. In this work, we give a microscopic description of this phenomenon, as well as an analogous two-dimensional system with a vortex. We solve the Dirac equation of electron field both analytically in continuum and numerically on a lattice, by adding the Wilson term and smearing...
In low temperature and high density region possible interesting phases are discussed from effective theories which exhibit the same symmetries as QCD, chiral symmetry.
They are pion condensation, color super conducting phases and inhomogeneous chiral condensation.
For spatial dependence of inhomogeneous chiral condensation, various kinds of structures are discussed; chiral density wave,...
Bayesian inference provides a rigorous framework to encapsulate our knowledge and uncertainty regarding various physical quantities in a well-defined and self-contained manner. Utilising modern tools, such Bayesian models can be constructed with a remarkable flexibility, leaving us totally free to carefully choose which assumption should be strictly enforced and which should on the contrary be...
We describe a first-principles method to apply lattice QCD to compute the order $\alpha_{\mathrm{EM}}$ corrections to $K\to\pi\ell\nu_\ell$ decay. This method formulates the calculation in infinite volume with the conventional infinite-volume, continuum treatment of QED. Infinite volume reconstruction is used to replace the QCD components of the calculation with finite-volume amplitudes...
The electromagnetic polarizability is an import property of nucleon. It describes the reponse of a nucleon when it is placed in an external eletric or magnetic field. The polarizability can be extracted from the real or virtual Compton scattering process γN → γN. We develop a method to calculate the the Compton scattering matrix elements of nucleon from a 4-point correlation function on the...
The continued generation of $n_f=2+1$ quark flavor gauge configurations using stabilized Wilson fermions by the open lattice initiative (OpenLat) is reported. We present the status of our ongoing production and show updates on increasing statistics at the four lattice spacings $a=0.12, 0.094, 0.077$ and $0.064$ fm. Aside from the flavor symmetric point we discuss advancements in going towards...
In this talk, we present the equivalence between the Wilson flow and the stout smearing. The similarity between these two methods was first pointed out by Lüscher’s original paper on the Wilson flow. We first show the analytical equivalence of two methods, which indicates that the finite stout smearing parameter induces $O(a^2)$ correction. We secondly show that they remain equivalent in...
Motivated by attempts to quantum simulate lattice models with continuous Abelian symmetries using discrete approximations, we study an extended-O(2) model that differs from the ordinary O(2) model by the addition of an explicit symmetry breaking term. Its coupling allows to smoothly interpolate between the O(2) model (zero coupling) and a $q$-state clock model (infinite coupling). In the...
The entanglement entropy is a quantity encoding important features of strongly interacting quantum many-body systems and gauge theories, but its analytical study is still limited to systems with high level of symmetry. This motivates the search for efficient techniques to investigate this quantity numerically, by means of Monte Carlo calculations on the lattice. In this talk, we present a...
The fate of heavy quarkonia states in quark-gluon plasma is encoded in the temperature dependence of their spectral functions. Reconstruction of spectral functions from Euclidean lattice correlators is an ill-posed problem. Despite a variety of techniques developed recently, many questions remain unresolved. It is known that the situation may be improved using anisotropic ensembles that...
Two popular methods to reduce discretisation effects are Symanzik improvement and gauge field smearing in the Dirac operator. Tree-level $O(a^2)$-improved Wilson fermions can be obtained from $O(a)$-improved Wilson fermions by adding one dimension-6 operator to the action. For gauge field smearing one wants to avoid the situation when too much smearing leads to uncontrolled continuum...
We explore a general method based on four-point functions in lattice QCD. The electric polarizability ($\alpha_E$) of a charged pion has been determined from the method in a previous simulation. Here we focus on the magnetic polarizability ($\beta_M$) using the same quenched Wilson action on a $24^3\times 48$ lattice at $\beta=6.0$ with pion mass from 1100 to 370 MeV. The results from the...
Bayesian model averaging is a statistical method that allows for simple and methodical treatment of systematic errors due to model variation. I will summarize some recent results, including other model weights which can give more robust performance than the Akaike information criterion, as well as clarifying its use for data subset selection.
The phase diagram at finite density is of great interest. In the literature, calculations are dominated by rooted staggered fermions. In continuum QCD at finite isospin density, there is pion condensation transition. We observe the reminants of such transition at finite lattice spacings as well at nonzero baryon density. In this talk, we discuss how this can be attributed to the ambiguity of...
The absence of a mass gap in QED requires handling of the zero-momentum modes of photons in finite-volume spacetimes. Once the problematic zero-momentum modes are removed using some prescription, the associated finite-volume effects in an observable typically scale with inverse powers of the spatial extent, $1/L$. In this talk, I discuss the analytical evaluation of these effects through order...
The pion decay constant $F_\pi$ plays an important role in QCD
and in Chiral Perturbation Theory. It is hardly known, however,
that a corresponding constant exists in the Schwinger model with
$N_f \geq 2$ degenerate fermion flavors. In this case, the "pion"
does not decay and $F_\pi$ is dimensionless. Still, $F_\pi$ can be
defined by 2d analogies to the Gell-Mann--Oakes--Renner...
In the context of radiative corrections to pseudoscalar meson leptonic decay, it is well-known that the $\mathcal{O}(\alpha_{\mathrm{em}})$ corrections to the decay amplitude logarithmically diverges when the lepton mass goes to zero, a behavior known as collinear divergences. Since leptons are not massless, this is not per se a divergence of the process, but it greatly enhances the value of...
We present our study of real-time dynamics and dynamical quantum phase transition (DQPT) in the (1+1)-dimensional massive Thirring mode using matrix product states (MPSs). Lattice regularisation of this model with Kogut-Susskind fermions corresponds to the XXZ spin chain with the presence of a constant and a staggered magnetic fields. In this work, we implement methods of variational uniform...
Estimating the trace of the inverse of a large matrix is an important problem in lattice quantum chromodynamics. A multilevel Monte Carlo method is proposed for this problem that uses different degree polynomials for the levels. The polynomials are developed from the GMRES algorithm for solving linear equations. To reduce orthogonalization expense, the highest degree polynomial is a composite...
Recently, formalism has been derived for obtaining the physical amplitudes for $\gamma^\star \to3\pi$, $K \to3\pi$, and other electroweak three-body decays, from finite-volume matrix elements, which can be obtained from lattice QCD calculations of three-point correlation functions. The relation between the finite-volume quantities and the desired infinite-volume amplitudes requires solving...
The dominant contribution to the theoretical uncertainty in the extracted weak parameters of the Standard Model comes from the hadronic uncertainties in the electroweak boxes, i.e. $\gamma-W^\pm/Z$ exchange diagrams. A dispersive analysis relates the box diagrams to the parity-odd structure function, $F_3$, for which the experimental data either do not exist or belong to a separate isospin...
We present recent results of the Bielefeld-Parma collaboration on the
baryon number density at imaginary chemical potential with
(2+1)-flavors of HISQ fermions on Nt=4,6 and 8 lattices. Based on these
data we calculate Fourier coefficients by means of a Filon-type
quadrature. We discuss how the universal critical behavior is manifest
in the asymptotic behavior of the Fourier coefficients...
We present the analysis of two recently proposed noise reduction techniques, Hutch++$^{1}$ and XTrace$^{2}$, both based on inexact deflation. These methods were proven to have a better asymptotic convergence to the solution than the classical Hutchinson stochastic method. We applied these methods to the computation of the trace of the inverse of the Dirac operator with $O(a)$ improved...
The $O(N)$-Nonlinear Sigma Model (NLSM) is an example of field theory on a target space with non-trivial geometry. One interesting feature of NLSM is asymptotic freedom, which makes perturbative calculations interesting.
Given the successes in Lattice Gauge Theories, Numerical Stochastic Perturbation Theory (NSPT) is a natural candidate for performing high order computations also in the case...
The excitation of nucleons to resonance structures via electromagnetic interactions is crucial for enhancing our comprehension of strong interactions within the realm of quark confinement. Additionally, accurate knowledge of neutrino-nucleon scattering is vital for neutrino oscillation experiments. In this study, we present determinations of the nucleon electric form factor ($G_E(Q^2)$), the...
Recent investigations of tests of unitarity of the first row of the CKM matrix report roughly $3 \sigma$ tension. Nonperturbative calculations of the radiative corrections (RC) are needed to reduce the theory uncertainty in CKM matrix elements. Here we present the electroweak box contribution to the pion, kaon and neutron decays. For pion and kaon case, we present published results from eight...
Using $N_f=2+1$ QCD calculations at physical quark mass and purely imaginary baryon chemical potential, we locate Lee-Yang edge singularities in the complex chemical potential plane. These singularities have been obtained by the multi-point Padé approach applied to the net baryon number density. We recently used this approach to extract the correct scaling of singularities near the...
In this talk we study the Ising model living on a discretization of two dimensional anti-de Sitter space. Our numerical work uses tensor network methods based on matrix product states (MPS) and matrix product operator (MPO) constructions. We use DMRG techniques to obtain the ground state and investigate its properties. For the time evolution of the model , we use the TEBD algorithm and show...
We perform a lattice QCD calculation to study the behavior of the electromagnetic form factor of the pion, both in the spacelike and timelike region. At the heavier than physical pion mass of 284 MeV of this lattice, the rho meson is a narrow resonance that drives the pion-pion P-wave elastic interaction. As a preamble for future work studying the timelike form factor in the coupled channel...
Peripheral heavy-ion collisions are expected to exhibit magnetic fields with magnitudes comparable to the QCD scale, as well as non-zero baryon densities. Whereas lattice QCD at finite magnetic field can be simulated directly with standard algorithms, an implementation of real chemical potentials is hindered by the infamous sign problem. Aiming to shed light on the QCD transition and on the...
We present the results of our determination of the scalar content of the nucleon using various techniques to address the large computational cost of a direct calculation. The gradient flow is employed to improve the signal, combined with the stochastic calculation of the all-to-all propagator using the standard Hutchinson trace method. By using supervised machine learning, decision trees in...
In this talk, we investigate the Trotter evolution of an initial state in the Gross-Neveu model and hyperbolic Ising model in two spacetime dimensions, leveraging quantum computers. We identify different sources of errors prevalent in various quantum processing units and discuss challenges to scale up the size of the computation. We present benchmark results obtained from some platforms and...
We study a 3-dimensional SU(2) gauge theory with 4 Higgs fields which
transform under the adjoint representation of the gauge group,
that has been recently proposed by Sachdev et al. to explain the physics
of cuprate superconductors near optimal doping. The symmetric
confining phase of the theory corresponds to the usual
Fermi-liquid phase while the broken (Higgs) phase is associated...
Standard lattice calculations of the glueball spectrum rely on effective mass plots and asymptotic exponential fits of two-point correlators, and involve various numerical challenges.
In this work, we propose an alternative procedure to extract glueball masses, based on the computation of the smeared spectral densities that encode information about the towers of states with given quantum...
We obtain the equation of state (EoS) for two-color QCD at low
temperature and high density from the lattice Monte Carlo simulation.
Two-color QCD is a good toy model of a real three-color QCD. The advantage
to study this model is that the sign problem is absent even in a finite
density regime because of the pseudo-reality of the quark field. We find
that the speed of sound exceeds the...