Chronology Protection in anti-de Sitter

TL;DR

This paper investigates the relationship between chronology protection and fermionic unitarity in the half-BPS sector of AdS5×S5 via the LLM map. It shows that bulk closed timelike curves arise whenever the fermionic phase-space density ρ violates the Pauli bound 0≤ρ≤1, with the superstar and its anti- counterpart as explicit examples. The authors argue that unitarity in the dual N=4 SYM theory forbids such configurations, providing a concrete realization of chronology protection in string theory. They also outline how this mechanism might extend to broader droplet configurations and thermal states, suggesting future work to establish a general absence of CTCs within the admissible sector.

Abstract

We consider 1/2 BPS excitations of AdS(5)xS(5) geometries in type IIB string theory that can be mapped into free fermion configurations according to the prescription of Lin, Lunin and Maldacena (LLM). It is shown that whenever the fermionic probability density exceeds one or is negative, closed timelike curves appear in the bulk. A violation of the Pauli exclusion principle in the phase space of the fermions is thus intimately related to causality violation in the dual geometries.

Figures (1)

• Figure 1: Location of the naked singularity, the region with CTCs and the velocity of light surface (VLS) for the anti-superstar with $-L^2<Q<0$.