Axionic domain wall number related to U(1)$_{\rm anom}$ global symmetry

TL;DR

This paper proposes that string compactifications with an anomalous U(1) gauge symmetry can resolve the axionic domain wall problem and address global symmetry issues for the QCD axion at intermediate scales.

Contribution

It introduces a novel mechanism linking anomalous U(1) gauge symmetries in string theory to the axionic domain wall number, providing a solution to longstanding problems.

Findings

String compactifications with anomalous U(1) symmetries can avoid the axionic domain wall problem.

Such models can simultaneously address the gravity spoil of global symmetries.

The approach allows for a consistent QCD axion at intermediate scales.

Abstract

The QCD axion with $f_a$ at an intermediate scale, 10**9-10**12 GeV, seems in conflict with the gravity spoil of global symmetries and may face the axionic domain wall problem. We point out that the string compactifications with an anomalous U(1) gauge symmetry, allowing desirable chiral matter spectra, circumvent these two problems simultaneously.