Holographic signatures of resolved cosmological singularities

TL;DR

This paper demonstrates how quantum corrections to a classical Kasner-AdS metric resolve singularities, leading to a finite two-point correlator and revealing new long-distance effects in the dual field theory.

Contribution

It provides an explicit example of singularity resolution in holography using quantum-corrected metrics, extending AdS/CFT applicability to classically singular regimes.

Findings

Quantum corrections remove the pole in the correlator caused by singularities.

A new long-distance contribution to the correlator appears due to the resolved singularity.

Qualitative results are confirmed by numerical analysis in a companion paper.

Abstract

The classical gravity approximation is often employed in AdS/CFT to study the dual field theory, as it allows for many computations. A drawback is however the generic presence of singularities in classical gravity, which limits the applicability of AdS/CFT to regimes where the singularities are avoided by bulk probes, or some other form of regularisation is applicable. At the same time, quantum gravity is expected to resolve those singularities and thus to extend the range of applicability of AdS/CFT also in classically singular regimes. This paper exemplifies such a computation. We use an effective quantum corrected Kasner-AdS metric inspired by results from non-perturbative canonical quantum gravity to compute the 2-point correlator in the geodesic approximation for a negative Kasner exponent. The correlator derived in the classical gravity approximation has previously been shown to contain a pole at finite distance as a signature of the singularity. Using the quantum corrected metric, we show explicitly how the pole is resolved and that a new subdominant long-distance contribution to the correlator emerges, caused by geodesics passing arbitrarily close to the resolved classical singularity. In order to compute analytically in this paper, two key simplifications in the quantum corrected metric are necessary. They are lifted in a companion paper using numerical techniques, leading to the same qualitative results.