High scale inflation, model-independent string axion, and QCD axion with domain wall number one

TL;DR

This paper discusses how high-scale inflation impacts axion models, proposing that string theory's model-independent axion with an anomalous U(1) symmetry naturally solves the domain wall problem, especially for domain wall number one.

Contribution

It introduces a string-theoretic solution to the axion domain wall problem that remains effective under high-scale inflation scenarios.

Findings

High-scale inflation challenges traditional axion models.

Model-independent axion with anomalous U(1) symmetry resolves domain wall issues.

The approach is compatible with GUT-scale inflation.

Abstract

The recent BICEP2 result shows that the Universe once has gone through the vacuum with the GUT scale energy density. The implied high scale inflation nullifies the dilution idea of topological defects, strings and domain walls, of the axionic system. In particular, domain walls are disastrous if the domain wall problem with domain-wall number greater than 1 is present. We argue that the model-independent axion in string compactification with the anomalous U(1) gauge symmetry resolves the domain wall problem naturally with a symmetry principle.