Exploring the Invisible Universe at UC Irvine

This award funds the research activities of Professor Kevork N. Abazajian at the University of California, Irvine. The identity of dark matter and the masses of neutrinos remain unresolved, and answering these questions ties the physics of the smallest particles to the history of the Universe. Under this grant award, Professor Abazajian will investigate how such particles were produced in the early Universe and how their effects appear in astronomical data. Work of this kind serves the national interest by extending fundamental knowledge of the laws that govern matter and the cosmos. Under this award, Professor Abazajian will train graduate students and postdoctoral researchers, mentor undergraduates through the Cal-Bridge program, and share results with the public through talks and print and web-based media. More technically, Professor Abazajian will work at the interface of neutrino physics, dark matter, and cosmology. He will compute the production of sterile neutrino dark matter in the early Universe from the quantum kinetic equations, treating resonant production driven by lepton asymmetries and multiple-flavor mixing. He will study warm dark matter and its signatures, drawing on James Webb Space Telescope lensing and Lyman-alpha forest measurements. He will test the standard cosmological model through determinations of the neutrino mass scale and the number of neutrino species, and will assess how firmly these hold under relaxed assumptions. He will examine current cosmological tensions, including the Hubble tension, evidence for evolving dark energy, and disparities in the growth of cosmic structure, and will forecast instrument designs to improve indirect searches for dark matter decay. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.