Speaker
Description
Measurements of the Cosmic Microwave Background (CMB) have confirmed a nearly scale-invariant primordial spectrum of adiabatic perturbations, in which the density fluctuations of radiation, baryons, and dark matter are in phase. However, primordial perturbations may also include an isocurvature component, in which the relative density fluctuations of individual species such as dark matter (DM) deviate from the adiabatic mode. Such isocurvature modes provide a powerful probe of physics beyond standard model of particle physics, for instance, pre-inflationary QCD axion DM. In this talk, I will present the most up-to-date constraints on pre-inflationary axion DM isocurvature using CMB measurements from Planck, as well as from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), for both flat and tilted primordial spectra. I will then discuss the theoretical implications of these isocurvature constraints.