Defect CFTs and holographic multiverse

TL;DR

This paper explores the holographic duality of the multiverse by analyzing bubble fluctuations in a defect conformal field theory, revealing limitations of the current duality proposal and suggesting non-unitary theories might be necessary.

Contribution

It investigates the spectrum of fluctuations in a defect CFT related to multiverse holography, highlighting potential constraints on the duality and the role of non-unitary theories.

Findings

Spectrum behavior incompatible with unitary defect CFTs

Potential for non-unitary defect theories to match fluctuation spectra

Insights into holographic multiverse proposals

Abstract

We investigate some aspects of a recent proposal for a holographic description of the multiverse. Specifically, we focus on the implications on the suggested duality of the fluctuations of a bubble separating two universes with different cosmological constants. We do so by considering a similar problem in a 2+1 CFT with a codimension one defect, obtained by an M5-brane probe embedding in AdS_4x S^7, and studying its spectrum of fluctuations. Our results suggest that the kind of behavior required by the spectrum of bubble fluctuations is not likely to take place in defect CFTs with an AdS dual, although it might be possible if the defect supports a non-unitary theory.