Speaker:
Taewook Youn (University of Texas, Austin)
Host:
Doojin Kim
Location:
Address:
Mitchell Institute for Fundamental Physics & Astronomy
College Station, Texas 77843
In this talk, I propose Stepped Partially Acoustic Dark Matter (SPartAcous), a new class of
interacting dark sector models with a qualitatively new cosmological behavior that can simultaneously address
the two most important tensions in cosmological data, the H0 and S8 tensions. The defining element of this class
of models is an interacting dark radiation that includes a component with a light mass, which becomes nonrelativistic
close to the time of matter-radiation equality, and which interacts with a fraction of dark matter. This
generalizes the scenario known as Partially Acoustic Dark Matter (PAcDM) by adding a mass to one of its
massless dark radiation components. As the light component annihilates, the remaining dark radiation heats up,
leading to a step-like increase in Neff, which has been shown to significantly reduce the H0 tension. In addition,
the interaction with dark matter reduces the matter power spectrum at small scales and thus alleviates the S8
tension, while its eventual decoupling leaves the power spectrum at larger scales identical to ΛCDM.
Copyright © 2023. All rights reserved, Texas A&M University Trademark | Texas A&M University, College Station, Texas 77843