Gauge dependence of the AdS instability problem

TL;DR

This paper investigates how gauge choices affect the AdS instability problem, revealing that certain singularities are due to diverging redshift effects indicating a breakdown of linearized gravity, with implications for boundary gauge analyses.

Contribution

It provides a physical interpretation of gauge-dependent singularities in AdS instability as diverging redshift, clarifying the role of gauge choice in the two-time framework.

Findings

Diverging redshift signals breakdown of linearized gravity.

Gauge choice influences the presence of oscillating singularities.

Boundary gauge calculations show regular TTF results despite singularities.

Abstract

Previous work on the AdS instability problem within the two-time framework (TTF) has found an "oscillating singularity" whose presence depends on the gauge choice. We give a physical interpretation of this singularity as a diverging redshift between the boundary and the center of AdS. This signals a genuine breakdown of the linearized gravity. One can also identify the diverging redshift through a back-reaction calculation purely in the boundary gauge, where the TTF result stays regular.