Rethinking Axion Dark Matter

Abstract

When Peccei-Quinn symmetry breaks after inflation, domain walls will form in the axion field at the QCD crossover if there is more than one quark charged under the symmetry. Destabilized by quantum gravity effects, the collapse of the wall network creates relativistic axions, which subsequently turn non-relativistic and become dark matter. Accounting for this additional contribution requires the axion to be heavier than ~10 meV - a mass range little explored experimentally. We describe results from a new light-shining-through-walls search for such heavy axions.
[SciPost Phys. 15, 003 (2023); Phys. Rev. Lett. 134, 055001 (2025); 2603.15808]


About the Speaker

Prof. Subir SARKAR works at the interface of astrophysics & cosmology with fundamental physics — including cosmic rays, dark matter, inflation & neutrino physics. He is a member of the IceCube Neutrino Observatory & Cherenkov Telescope Array collaborations – as well as participating in the Rubin / LSST Dark Energy Science Collaboration and laboratory laser plasma experiments.

He obtained his PhD (1982) at the Tata Institute of Fundamental Research, Bombay. Since 1990, he has been at the Rudolf Peierls Centre for Theoretical Physics, Oxford where he headed the Particle Theory Group and is now Professor Emeritus. He was also Niels Bohr Professor (2013-18) at NBI, Copenhagen.


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