Fundamental cosmic strings

TL;DR

This paper explores the connection between cosmic strings and fundamental strings from superstring and M-theory, discussing recent developments, observational evidence, and future prospects.

Contribution

It highlights the potential role of macroscopic fundamental strings in the brane-world scenario as a modern perspective linking string theory with cosmic string phenomena.

Findings

Recent developments unify cosmic and fundamental strings.

Observational evidence constrains cosmic string models.

Future observations may detect signatures of fundamental strings.

Abstract

Cosmic strings are linear concentrations of energy that may be formed at phase transitions in the very early universe. At one time they were thought to provide a possible origin for the density inhomogeneities from which galaxies eventually develop, though this idea has been ruled out, primarily by observations of the cosmic microwave background (CMB). Fundamental strings are the supposed building blocks of all matter in superstring theory or its modern version, M-theory. These two concepts were originally very far apart, but recent developments have brought them closer. The `brane-world' scenario in particular suggests the existence of macroscopic fundamental strings that could well play a role very similar to that of cosmic strings. In this paper, we outline these new developments, and also analyze recent observational evidence, and prospects for the future.