Weinberg Institute Seminar with Masha Baryakhtar

Abstract: Theories that seek to answer the outstanding questions in particle physics often predict new, light, feebly-interacting particles. The QCD axion is one example of such a beyond-the-standard-model particle: it elegantly solves the strong-CP problem and can be the dark matter in our universe. I will focus on the fundamental coupling of the axion to gluons, which is particularly difficult to test in the lab and is currently best constrained by extreme astrophysical environments such as neutron stars.  If the axion mass is exceptionally light in vacuum, existing neutron star crust observations already constrain axion parameter space close to the QCD line. I will describe how in these extremely dense environments, the axion mass can become negative, resulting in axion condensation and in turn affecting nuclear matter and neutron star structure. I will also comment on ongoing work on the properties of nuclear matter with a QCD-$\theta$ angle of $\pi$ and potential implications for the QCD axion.

Bio: Masha Baryakhtar is an Assistant Professor at the University of Washington. Born in Kharkiv, Ukraine, she moved to the U.S. in middle school. Before arriving in Seattle, Baryakhtar received her PhD from Stanford University, and held Postdoctoral Fellowships at Perimeter and NYU. Professor Baryakhtar's research focuses on theories beyond the Standard Model of particle physics and on creating new directions for testing them. She is pursuing the theoretical development of precision laboratory searches for dark matter, as well as new particle searches in the extreme environments of black holes, neutron stars, and the early universe. Baryakhtar's work has been recognized by honors including the Aspen Block Award, Frontiers of Science Award, Simons Emmy Noether Faculty Fellowship, and DOE Early Career Award.