In this talk, I will introduce a conceptually new cosmological scenario in which the dark matter (DM) of the universe is made of an ensemble of continuum states. The consistency with late time observations, such as CMB and large scale structure formation, requires that the spectral density of the continuum needs to be gapped, i.e. the spectrum starts at some finite mass scale. I will discuss how physics of the gapped continuum can be described in QFT and show that it can be obtained as a holographic effective action of 5D EFT in a soft-wall background. Phenomenology of continuum dark matter is remarkably novel and interesting. It makes weak scale DM coupled to standard model gauge forces consistent with all experimental constraints and yet can be fully tested. This is to be contrasted with the situation for its particle-cousin: particle-WIMP is ruled out completely. In addition, the nature of continuum DM leads to late decays of heavy modes to light mode plus SM particles. This may alter the ionization history of the universe and results in a lower bound on the effective coupling. At direct detection, again the continuum makes a huge difference. A special continuum kinematics leads to a significant suppression of the cross section, reviving the idea of WIMP. Overall, a simple change in concept, “particle → continuum”, opens up a completely new “axis” in DM theory space, with many surprising signatures.
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