Physical Society Colloquium

The search for axion dark matter

Benjamin Safdi

Physics Department
UC Berkeley

The quantum chromodynamics axion and axion-like particles are some of the most sought-after beyond the Standard Model particles at present because of their possible connections with the strong-CP problem, dark matter, and ultraviolet physics such as Grand Unification and String Theory. Laboratory searches are underway around the world to search for these hypothetical particles. However, these searches are notoriously difficult because the axion mass is currently unknown. The axion mass is in principle calculable by solving the axion dynamics in the early Universe, but such calculations are made difficult by nonlinear effects in the equations of motion. I will show how state-of-the-art supercomputing facilities are being leveraged to simulate axion cosmology and inform axion experiments. The early Universe simulations are part of a broader program, which I will overview, to rule out or confirm the existence of the axion in nature in the coming years. This broad program ranges from precision laboratory experiments such as ABRACADABRA to studies of small changes in the cooling rates of stars.