Continuum Dark Matter
Dr. Sungwoo Hong
Postdoctoral Researcher
U Chicago
In this talk, I will introduce a conceptually new cosmological scenario in which the dark matter (DM) 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. This means that 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, one central feature being "continuum kinematics", which I will explain. It makes weak scale DM coupled to standard model gauge forces (e.g. Z-boson) consistent with all experimental constraints and yet can be fully tested. This is to be contrasted with the situation for its particle-counterpart: particle-WIMP coupled to Z-boson 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, resulting 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 "Weakly Interacting" Continuum (as opposed to Massive Particle). Overall, a simple change in concept, “particle → continuum”, opens up a new “axis” in DM theory space, with many surprising signatures.
This will be a zoom talk via the link: https://notredame.zoom.us/j/92798673921?pwd=THlnTmo1a0FMZlIycnVtVzVrL2ZyQT09