PIRSA:25110076

What is the QCD axion mass?

Benabou, J. (2025). What is the QCD axion mass?. Perimeter Institute. https://pirsa.org/25110076

Benabou, Joshua. What is the QCD axion mass?. Perimeter Institute, Nov. 11, 2025, https://pirsa.org/25110076 

          @misc{ pirsa_PIRSA:25110076,
            doi = {10.48660/25110076},
            url = {https://pirsa.org/25110076},
            author = {Benabou, Joshua},
            keywords = {Particle Physics},
            language = {en},
            title = {What is the QCD axion mass?},
            publisher = {Perimeter Institute},
            year = {2025},
            month = {nov},
            note = {PIRSA:25110076 see, \url{https://pirsa.org}}
          }

Joshua Benabou

Talk numberPIRSA:25110076
DOI10.48660/25110076
Collection
Talk Type Scientific Series
Subject

Abstract

The QCD axion may solve the strong CP problem and constitute the dark matter (DM) abundance in our Universe. Peccei-Quinn (PQ) axions may form axion strings if the PQ phase transition occurs after inflation. I will discuss recent advances in the computation of the QCD axion DM mass in this scenario from the most precise and accurate lattice simulations to-date of axion-string networks, leading to a predicted mass range of 40 - 300 µeV. On the other hand, string theory axions, which are compelling solutions to the PQ quality problem, do not generically form strings - except in special inflationary paradigms such as brane inflation - meaning that there is no unique predicted value for the QCD axion DM mass. Nonetheless, if a Grand Unified Theory is assumed, I will explain why in broad regions of the string landscape, the mass of a stringy QCD axion is expected to be ~ 0.01 to 10 neV, independently of its DM fraction.