David J.E. Marsh (Georg-August-Universität Göttingen, Institute for Astrophysics)
Axions and axion-like particles are excellent dark matter candidates, spanning a vast range of mass scales from 1e-2 eV for the QCD axion, to 1e-22 eV for ultralight axions in string theory. I will discuss astrophysical and cosmological constraints on axions at either end of this spectrum, using gravitational microlensing in the local Universe, cosmic microwave background anisotropies, and galaxy formation. Direct detection at the extremes of axion parameter space is challenging. I will discuss bounds on ultralight axions derived from time variation of the neutron electric dipole moment, and various new ideas for QCD axion detection at high frequency.
(Host: Luca Visinelli)