The circular loop equation of a cosmic string with time-varying tension in de Sitter spacetimes

TL;DR

This paper investigates the dynamics of circular cosmic string loops with time-varying tension in de Sitter spacetime, revealing conditions under which they avoid collapsing into black holes based on initial size and tension variation.

Contribution

It introduces a new analysis of cosmic string loop evolution with time-dependent tension in de Sitter space, identifying critical initial sizes and tension power laws that prevent black hole formation.

Findings

Loops with initial radius > 0.707L do not form black holes.

Loops with initial radius < 0.707L and low enough tension power also avoid collapse.

The tension's dependence on cosmic time influences black hole formation thresholds.

Abstract

In this work the equation of circular loops of cosmic string possessing time-dependent tension is studied in the de Sitter spacetime. We find that the cosmic string loops with initial radius $r(t_{0})>0.707L$, L de Sitter radius, should not collapse to form a black holes. It is also found that in the case of $r(t_{0})<0.707L$ a loop of cosmic string whose tension depends on some power of cosmic time can not become a black hole if the power is lower than a critical value which is associated with the initial size of the loop.