Eur. Phys. J. Plus (2014) 129: 257
https://doi.org/10.1140/epjp/i2014-14257-1

Regular Article

World-sheet stability, space-time horizons and cosmic censorship

V.A. Steklov Mathematical Institute, Russian Academy of Sciences, Ulitsa Gubkina 8, 119991, Moscow, Russia

^* e-mail: mdp30@cam.ac.uk

Received: 13 September 2014
Accepted: 27 October 2014
Published online: 27 November 2014

Abstract

Previously, we have analyzed the stability and supersymmetry of the heterotic superstring world sheet in the background Friedmann space-time generated by a perfect fluid with energy density ρ and pressure p = (γ − 1) ρ. The world sheet is tachyon-free within the range 2/3 ≤ γ ≤ ∞, and globally supersymmetric in the Minkowski-space limit ρ = ∞, or when γ = 2/3, which is the equation of state for stringy matter and corresponds to the Milne universe, that expands along its apparent horizon. Here, this result is discussed in greater detail, particularly with regard to the question of horizon structure, cosmic censorship, the TCP theorem, and local world-sheet supersymmetry. Also, we consider the symmetric background space-time generated by a static, electrically (or magnetically) charged matter distribution of total mass and charge Q, and containing a radially directed macroscopic string. We find that the effective string mass m satisfies the inequality m ² ≥ 0, signifying stability, provided that , which corresponds to the Reissner-Nordström black hole. The case of marginal string stability, m ² = 0, is the extremal solution , which was shown by Gibbons and Hull to be supersymmetric, and has a marginal horizon. If , the horizon disappears, m ² < 0, and the string becomes unstable.