Gravitational wave and dark matter from Axion-Higgs string

TL;DR

This paper investigates axion-Higgs cosmic strings as sources of dark matter and gravitational waves, providing bounds on axion parameters and analyzing the detectability of resulting gravitational wave signals.

Contribution

It presents lattice simulations of axion-Higgs strings and evaluates their implications for dark matter abundance and gravitational wave signals, including observational constraints.

Findings

Axion dark matter from strings can overproduce dark matter if parameters are not constrained.

Predicted gravitational wave spectra are below the sensitivity of current pulsar timing arrays.

Bounds on axion decay constant and mass are derived from cosmological and observational considerations.

Abstract

Axions have long been considered plausible candidates for dark matter. The axion dark matter emitted from cosmic strings after the Peccei-Quinn (PQ) symmetry breaking in the early Universe was extensively simulated. In this work, we study dark matter and gravitational waves through the lattice simulation of the Axion-Higgs string. We gave the dark matter overproduction and the Big Bang nucleosynthesis bounds on the axion decay constant $f_a$ and the axion mass $m_a$ for axion-like particles, and found that the predicted gravitational wave spectra cannot be probed by the dataset of the current pulsar timing array experiments.