Stringy Cosmic Strings and Axion Cohomology

TL;DR

This paper investigates axion-charged cosmic string solutions in string theory, revealing unique black string configurations with horizons and discussing their relation to sigma models and cosmic censorship.

Contribution

It constructs the most general exact solutions for axion-charged cosmic strings and proves no-hair theorems, highlighting their connection to gauged WZWN sigma models.

Findings

Axion charge induces nontrivial gravitational configurations with horizons.

Uniqueness of black string solutions is established through no-hair theorems.

Solutions relate to gauged WZWN models, supporting cosmic censorship.

Abstract

The static stationary axially symmetric background ("infinite cosmic string") of the $D=4$ string theory provided with an axion charge is studied in the effective theory approach. The most general exact solution is constructed. It is found that the Kalb-Ramond axion charge, present in the string topology $R^{3} \times S^{1}$, produces nontrivial gravitational field configurations which feature horizons. The corresponding ``no-hair'' theorems are proved which stress uniqueness of black strings. Connection of the solutions with the gauged WZWN sigma model constructions on the world sheet is discussed since they are the only target spaces which hide their singularities behind horizons, and thus obey the cosmic censorship conjecture.