Quasinormal modes and holographic correlators in a crunching AdS geometry

TL;DR

This paper computes exact and numerical holographic correlators in a crunching AdS background, revealing how deformation affects quasinormal modes and correlator structures, with implications for de Sitter holography.

Contribution

It provides the first exact frequency space correlators in a crunching AdS background and analyzes the deformation's impact on quasinormal modes and correlator patterns.

Findings

Exact correlators for massless scalars in the deformed background.

Pattern of quasinormal poles varies with deformation, including critical points.

In the infinite deformation limit, scalar spectra become identical.

Abstract

We calculate frequency space holographic correlators in an asymptotically AdS crunching background, dual to a relevant deformation of the M2-brane CFT placed in de Sitter spacetime. For massless bulk scalars, exploiting the connection to a solvable supersymmetric quantum mechanical problem, we obtain the exact frequency space correlator for the dual operator in the deformed CFT. Controlling the shape of the crunching surface in the Penrose diagram by smoothly dialling the deformation from zero to infinity, we observe that in the large deformation limit the Penrose diagram becomes a `square', and the exact holographic correlators display striking similarities to their counterparts in the BTZ black hole and its higher dimensional generalisations. We numerically determine quasinormal poles for relevant and irrelevant operators, and find an intricate pattern of these in the complex frequency plane. In the case of relevant operators, the deformation parameter has an infinite sequence of critical values, each one characterised by a pair of poles colliding and moving away from the imaginary frequency axis with increasing deformation. In the limit of infinite deformation all scalar operators have identical quasinormal spectra. We compare and contrast our strongly coupled de Sitter QFT results with strongly coupled thermal correlators from AdS black holes.