Cosmic strings reborn?

TL;DR

Cosmic strings are reconsidered as viable relics of high-energy physics due to potential links with fundamental string theory and tantalizing observational hints. The paper reviews their formation and evolution, distinctive gravitational effects (notably a conical spacetime with deficit angle) and associated lensing signals, and the string-theory realizations that could yield macroscopic strings (F- and D-strings) with nontrivial intercommutation. It evaluates candidate observations (CSL-1 lensing and a near-field oscillating loop in Q0957+561) against current bounds on $G\mu$, and discusses future prospects through gravitational-wave detections and refined theoretical predictions. The work argues that even modest string contributions could be detectable with upcoming observations, warranting continued theoretical and observational effort.

Abstract

There are two main reasons for the recent renewal of interest in cosmic strings: Fundamental string-theory models suggest their existence; and there are at least two tentative observations of their possible effects. In this talk, I review their current status in the light of these two factors.