Reduced Axion Abundance from an Extended Symmetry

Understand

In recent work we showed that the relic dark matter abundance of QCD axions can be altered when the Peccei-Quinn (PQ) field is coupled to very light scalar/s, rendering the effective axion mass dynamical in the early universe.

• In this work we develop this framework further, by introducing a new extended symmetry group to protect the new particles' mass.
• We find that with a new global $SO(N)$ symmetry, with large $N$, we can not only account for the lightness of the new scalars, but we can reduce the axion relic abundance in a technically natural way.
• This opens up the possibility of large PQ scales, including approaching the GUT scale, and still naturally producing the correct relic abundance of axions.