Explorations in the Cosmic and Particle Universe
Dr. Caner Ünal
Abstract
In the first part of this talk, I will discuss the phenomenology of axion-gauge field couplings during inflation through density perturbations and gravitational waves (GWs), connecting these mechanisms with probes of small-scale inflationary perturbations via cosmic microwave background (CMB) spectral distortions and GW interferometers. In the second part, I will focus on probing light bosons—even if they constitute a subdominant fraction of dark matter—across various mass regimes: $10^{-26}$ to $10^{-23}\text{ eV}$ via pulsar timing arrays, up to $10^{-21}\text{ eV}$ via the halo mass function, $10^{-21}$ to $10^{-17}\text{ eV}$ via supermassive black hole superradiance, and $10^{-21}$ to $[10^{21}]\text{ eV}$ via primordial black hole superradiance. I will conclude by outlining immediate and long-term future research directions.
Short Bio
Caner Ünal holds double-major B.S. degrees in Physics and Electrical & Electronics Engineering from Middle East Technical University (METU). He earned his Ph.D. in Theoretical Cosmology and High Energy Physics from the University of Minnesota under the supervision of Prof. Marco Peloso. Following his doctoral studies, he conducted postdoctoral research with the CEICO group at the Czech Academy of Sciences in Prague, and subsequently at Ben-Gurion University as a recipient of both the Kreitman Postdoctoral Fellowship and IASH Excellence Fellowship. Currently, he is a senior research fellow at METU. His research interests span early universe cosmology, cosmological perturbations, axion physics, stochastic gravitational wave backgrounds, primordial black holes, high-energy astrophysics, and black hole superradiance. He has authored works accumulating over 2,000 citations (with an average exceeding 117 citations per paper) and contributes as a theorist to major international collaborations, including NANOGrav (North American Nanohertz Observatory for Gravitational Waves), the Square Kilometre Array (SKA), and Cosmic Explorer (CE).
