NBIA Seminar: Anupam Ray

Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the very early universe, are one of the earliest proposed and viable dark matter (DM) candidates. PBHs can make up a large or even entirety of DM over a wide range of masses. Ultralight PBHs in the mass range of 10^{15} - 10^{17} g, emit particles via Hawking radiation, act as a decaying DM, and can be probed via observations of those emitted particles in various space as well as ground based detectors. In this talk, I will discuss how diffuse supernova neutrino background searches at the Super-Kamiokande neutrino observatory, and measurement of the 511 keV gamma-ray line by INTEGRAL telescope can set robust, world-leading exclusions on the fraction of DM composed of ultralight PBHs. 21-cm cosmology also provides an exciting avenue to explore ultralight PBHs. I will show how EDGES measurement of the global 21-cm signal can be translated to set stringent exclusions on ultralight PBHs as DM. Finally, I will also outline how observations of low energy Galactic Center photons by the imminent soft gamma-ray telescopes, such as AMEGO, can probe the completely unexplored asteroid mass window where PBHs can be all of DM.