Axion cosmology with long-lived domain walls

Understand

We investigate the cosmological constraints on axion models where the domain wall number is greater than one.

• In these models, multiple domain walls attached to strings are formed, and they survive for a long time.
• Their annihilation occurs due to the effects of explicit symmetry breaking term which might be raised by Planck-scale physics.
• We perform three-dimensional lattice simulations and compute the spectra of axions and gravitational waves produced by long-lived domain walls.