The Axion Quality Problem: Global Symmetry Breaking and Wormholes

Understand

Continuous global symmetries are expected to be broken by gravity, which can lead to important phenomenological consequences.

• A prime example is the threat that this poses to the viability of the Peccei-Quinn solution to the strong CP problem.
• In this paper, we explore the impact of wormholes as a source of global symmetry breaking by gravity.
• We review the current status of wormholes and global symmetries and note that, surprisingly, the axion has a quality problem within non-perturbative Einstein gravity.