Hot Topics on the Cosmic Frontier

    • Colloquium 1
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        New cosmic frontiers

        This talk will summarize several current issues and new possibilities in cosmology. In particular, I will discuss (briefly) the possibility to seek new physics with line intensity mapping and with kSZ tomography; prospects for new calculational techniques in cosmological perturbation theory; and the Hubble tension and early dark energy.

        Speaker: Marc Kamionkowski (Johns Hopkins University)
      • 2
        Cosmology with Hundreds of Millions of Spectra in the 2030's

        DESI and the Rubin Observatory will provide data for exquisite measurements of the distance-redshift relation and growth of structure. While these observations will significantly advance our understanding of dark energy and the cosmological model, a vast amount of information will still be available for spectroscopic observation. At redshifts z>1.5, spectroscopic clustering will be far from cosmic-variance limited on all scales, leaving potential for future measurements of inflationary physics, the BAO distance scale, and growth of structure. At lower redshifts, the Stage-IV experiments will offer lensing and spectroscopy for precise distance and growth measurements at linear and quasi-linear scales, but even larger samples will still be possible to explore cosmological information from smaller scales. Several new facilities have been proposed that offer at least an order of magnitude increase in spectroscopic capability over existing programs, thus allowing a Stage-V optical/infrared spectroscopic program to advance the cosmological model over the redshift range 0<z<4. In this talk, I will present these designs and provide a high-level overview of the science cases that can be pursued with such a facility.

        Speaker: Kyle Dawson (University of Utah)
    • Colloquium 2
      • 3
        Direct Dark Matter Detection

        The search for particle dark matter has seen tremendous progress and developments in the last decade. One of the primary methods for understanding the particle nature of dark matter is through direct detection. In this talk, I will provide an overview of the progress made in dark matter direct detection, discuss the synergies with other probes for dark matter, and give a look at what we can hope to see in the next decade.

        Speaker: Tien-Tien Yu (University of Oregon)
      • 4
        Messengers and Fundamental Physics

        Below the geographic South Pole, the IceCube project has transformed one cubic kilometer of natural Antarctic ice into a neutrino detector. IceCube detects more than 100,000 neutrinos per year in the GeV to 10 PeV energy range. From those, we have isolated a flux of high-energy neutrinos of cosmic origin, with an energy flux that is comparable to that of high-energy photons. We have also identified the first sources pointing at supermassive black holes in active galaxies as the sources of high energy neutrinos (and cosmic rays!). Studies of the cosmic neutrino beam as well as the high-statistics background of atmospheric neutrinos provide powerful opportunities for studying the neutrinos themselves.

        Speaker: Francis Halzen (University of Wisconsin)
      • 5
        Probing Fundamental Physics with the Gravitational Wave Universe

        Beginning with the first detection of black hole mergers in 2015, we now have a new probe of physics from the gravitational sector. Plans are underway for a host of new observatories and quantum-metrology-enhanced upgrades. The coverage of the GW sky from frequencies of nHz to kHz, will enable exploring: gravitational cosmography, phase transitions in the early universe, the QCD phase transition and measure EOS of dense nuclear matter, explore the nature of the cosmological constant, physics beyond the standard model, and tests of the structure of spacetime. These next big steps in GW detectors will require large scale collaborations, and instrumentation collaborations with the high energy physics and quantum information communities.

        Speaker: Rana Adhikari (Caltech)
    • Colloquium 3
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        Wave Dark Matter: Quantum Enabled Opportunities for Discovery

        Despite robust evidence for the existence of dark matter, questions regarding its precise nature endure. Bosonic dark matter candidates with low mass can be well-described as classical waves. Axions are one particularly compelling form of bosonic dark matter because of their ability to compose all the missing matter and solve the strong CP problem. The direct detection of 'wave-like' dark matter calls for unique experimental designs and technology. With the development and proliferation of quantum devices, new possibilities have emerged in recent years. Indeed, direct detection searches for axions have already benefitted from the implementation of quantum amplifiers in their receiver chain, enabling the achievement of DFSZ sensitivity. We explain the motivation to search for wave-like dark matter and opportunities to leverage advancements in quantum technology with the goal of direct dark matter detection. We present recent bounds on the mass for wave-like dark matter as set by theory and experiment and set forth a cohesive strategy to search for possible candidates with increasing sensitivity.

        Speaker: Chelsea Bartram (University of Washington)
      • 7
        Indirect Detection of Dark Matter

        All the evidence to date for dark matter comes from its fingerprints in astrophysics and cosmology. This affords indirect detection searches an exciting opportunity not available with terrestrial probes: the chance to test dark matter in its natural habitat. In this talk I will discuss the path toward to dark matter discovery with indirect detection, emphasizing the important role of astrophysical studies in the coming years, and highlighting the importance of enabling discovery with complementary measurements.

        Speaker: Rebecca Leane (SLAC)
      • 8
        Cosmic probes of dark matter

        Cosmological and astrophysical measurements have so far provided the only robust, positive empirical measurements of dark matter, and can provide wide-ranging insight into their properties, spanning ~90 orders of magnitude in dark matter mass. I will review a variety of cosmic probes of dark matter, which are able to
        distinguish models with different microphysical properties, using tracers as diverse as exoplanets, dwarf galaxies, neutron stars, clusters, and large-scale structure that probe the properties of dark matter halos and extreme environments. Large multi-wavelength astrophysical surveys coming online this decade will accelerate this search, in a way that is complementary to other dark matter probes.

        Speaker: Risa Wechsler (SLAC)
    • Colloquium 4
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        Cosmology and Fundamental Physics with the Cosmic Microwave Background

        The Cosmic Microwave Background (CMB) encodes a wealth of signals which inform cosmology and fundamental physics. Improved measurements will constrain primordial gravitational waves providing new insights into the ultra high energy physics of the early universe; give new constraints on the dark universe providing evidence for, or ruling out light relativistic degrees of freedom including many other well motivated candidates; map the distribution of matter through gravitational lensing and the Sunyaev–Zeldovich effects providing constraints on dark energy, neutrinos and other phenomena; and measure the time varying millimeter wave sky. In this talk I review the science goals for CMB measurements and give an overview of ongoing and developing efforts with a particular emphasis on CMB-S4 the CMB communities planned next generation experiment.

        Speaker: Jeff McMahon (University of Chicago)
      • 10
        High Energy Physics with Astrophysical Gamma Rays

        Astrophysical gamma rays from 511 keV up to greater than 1 PeV have been detected from multiple sources and serve as unique probes of high energy physics. The existence of the highest energy gamma rays constrains Lorentz invariance violation beyond the Plank mass scale. Signatures of various forms of dark matter can also be discovered with gamma ray observations. Gamma rays from distant sources constrain the existence of Axion Like Particles into which they could transform via interactions with magnetic fields. Primordial black holes, a possible fractional constituent of the dark matter, evaporate via Hawking radiation to produce transient gamma ray sources. And WIMP dark matter is predicted to annihilate with itself producing gamma ray lines of energy equal the dark matter mass as well as a lower energy continuum. Searches for such gamma rays from locations known to be rich in dark matter have ruled out WIMPs of a range of masses that annihilate into gamma rays with a similar cross-section as those in the early universe. The unexplained excess of 511 keV emission from our galaxy could also be a signature of positrons produced by dark matter. In the next decade, planned and existing gamma ray detectors will further explore these and other fundamental high energy physics phenomena.

        Speaker: Brenda Dingus (Los Alamos National Lab)
      • 11
        Intensity Mapping for Cosmology

        Intensity mapping is a catch-all term encompassing experimental techniques that map the universe without identifying individual objects and instead measuring large-scale fluctuations in the aggregate intensity from many objects. It is commonly used at low frequencies where limited instrumental resolution does not allow identification of individual objects or when signal to noise is insufficient to do unequivocally. I'll present results from this emerging technique in 21cm and molecular line mapping and briefly mention potential applications in optical. Experiments based on intensity mapping require further development to enable them to reach their full potential, but could offer potentially revolutionary gains in cost efficiency of mapping distant universe and thus enable transformative advances in our understanding of the Universe.

        Speaker: Anze Slosar (BNL)