Abstract
We study early and late time signatures of both QCD axion strings and hyperlight axion strings (axiverse strings). We focus on charge deposition onto axion strings from electromagnetic fields and subsequent novel neutralizing mechanisms due to bound state formation. While early universe signatures appear unlikely, there are a plethora of late time signatures. Axion strings passing through galaxies obtain a huge charge density, which is neutralized by a dense plasma of bound state Standard Model particles forming a one dimensional “atom”. The charged wave packets on the string, as well as the dense plasma outside, travel at nearly the speed of light along the string. These packets of high energy plasma collide with a center of mass energy of up to 109 GeV. These collisions can have luminosities up to seven orders of magnitude larger than the solar luminosity, and last for thousands of years, making them visible at radio telescopes even when they occur cosmologically far away. The new observables are complementary to the CMB observables for hyperlight axion strings that have been recently proposed, and are sensitive to a similar motivated parameter range.
Highlights
Axions are one of the most compelling candidates for new physics [1,2,3,4,5]
We studied in detail some observable consequences of axion strings coming from the effect electromagnetic fields have on an axion string as the they pass by the string
The passing magnetic field moves charge from the axion profile around the string to the superconducting axion string core. This charge movement is a consequence of the beautiful physics of anomaly inflow [19,20,21] and the superconductivity of axion strings has been explored by seminal papers in the 1980s [7,8,9,10]
Summary
Axions are one of the most compelling candidates for new physics [1,2,3,4,5]. They are robustly predicted in many UV completions of the Standard Model, and can naturally solve the strong CP problem [1,2,3] and be dark matter. As well as early universe scattering processes, can lead to charged axion string cores that can have macroscopic charge and current densities, which results in extremely large electromagnetic fields around the string. The high electric fields of a charged axion string can ionize surrounding gas and cause rapid production of SM particles around the string core due to, for example, stimulated Schwinger pair production [25,26,27] and the Blandford-Znajek process [28]. This populates a dense cloud of charged particles with density as large as λ3Q. In appendix C, we review some of the effects we discuss from a condensed matter perspective, and point out the key differences between our systems and the corresponding condensed matter systems
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