The Flow Around a Cosmic String, Part I: Hydrodynamic Solution

TL;DR

This paper derives the hydrodynamic solution for gas flow around a cosmic string, revealing shock formation, gas heating, and potential observational signatures like HI line emissions and large-scale radio sources.

Contribution

It provides the first analytical solution for supersonic gas flow past a cosmic string, including shock formation and observable effects, expanding understanding of cosmic string interactions.

Findings

Gas flow forms two planar shocks with variable compression ratios.

Gas heating and overdensity occur in an unusual wedge shape detectable via HI lines.

Particle acceleration may happen when strings cross hot gas in galaxy clusters.

Abstract

Cosmic strings are linear topological defects which are hypothesized to be produced during inflation. Most searches for strings have been relying on the string's lensing of background galaxies or CMB. In this paper I obtained the solution for the supersonic flow of the collisional gas past the cosmic string which has two planar shocks with shock compression ratio that depend on the angle defect of the string and its speed. The shocks result in compression and heating of the gas and, given favorable condition, particle acceleration. The gas heating and overdensity in an unusual wedge shape can be detected by observing HI line at high redshifts. The particle acceleration can occur in present-day Universe when the string crosses the hot gas contained in galaxy clusters and, since the consequences of such collision persist for cosmological timescales, could be located by looking at the unusual large-scale radio sources situated on a single spatial plane.