Axiverse Strings

TL;DR

This paper explores the properties of axiverse cosmic strings arising from string theory, highlighting their potential to connect to moduli space boundaries and produce observable effects like variations in fundamental constants.

Contribution

It analyzes the structure and signatures of axiverse cosmic strings, emphasizing their role as portals to moduli space boundaries and their potential observable consequences.

Findings

String axiverse cosmic strings have cores that connect to moduli space boundaries.

These strings exhibit tension with a logarithmic dependence on inter-string separation.

Potential observable effects include variations in SM parameters and violations of the equivalence principle.

Abstract

If the QCD axion solves the strong CP problem then light axion-like-particles (ALPs) are expected to be ubiquitous in string theory - the string axiverse. Such ALPs can be the QCD axion and constitute dark matter (DM) or radiation, quintessence, and lead to new forces. String ALPs are also expected to give rise to a multiplicity of cosmologically important global axion strings. We study the properties of these axiverse cosmic strings including the vital effects of moduli stabilization, and find that the string cores provide `portals' to different decompactifications - to be precise, the cores explore the large K\"ahler or complex structure boundary of moduli space. As usual for global strings the tension $T_1\sim \Lambda^2 \log(L\Lambda)$ with inter-string separation, $L$, while $\Lambda$ can be small $\ll M_{\rm pl}$. At long distances from the string there are potential new signatures involving variations in Standard Model (SM) parameters (Yukawa couplings, gauge couplings, masses) and equivalence principle violations.