Chronology Protection in AdS/CFT

TL;DR

This paper discusses how string theory, through the AdS/CFT correspondence, provides a mechanism to prevent time travel paradoxes in certain geometries by linking unitarity in fermion models to chronology protection.

Contribution

It demonstrates that unitarity in free fermion models within AdS/CFT ensures the preservation of causality in the dual string theory geometries.

Findings

Unitarity of free fermion systems correlates with chronology protection.

String theory in the half BPS sector prevents closed timelike curves.

AdS/CFT provides a framework linking quantum unitarity and causality.

Abstract

We review the issue of chronology protection and show how string theory can solve it in the half BPS sector of AdS/CFT. According to the LLM prescription, half BPS excitations of AdS_5 x S^5 geometries in type IIB string theory can be mapped into free fermion configurations. We show that unitarity of the theory describing these fermions is intimately related to the protection of the chronology in the dual geometries.