Semi-classical BMS$_3$ blocks and flat holography

TL;DR

This paper constructs BMS$_3$ blocks in 2D field theory, compares them with flat space holographic computations, and explores implications for flat holography and eigenstate thermalization.

Contribution

It generalizes the monodromy method for BMS symmetry and introduces geodesic Feynman diagrams in flat geometries for holographic analysis.

Findings

BMS$_3$ blocks constructed in 2D field theory.

Comparison with holographic geodesic diagrams shows agreement.

Implications for eigenstate thermalization in flat holography.

Abstract

We present the construction of BMS$_3$ blocks in a two-dimensional field theory and compare the results with holographic computations involving probe particles propagating in flat space cosmologies. On the field theory side, we generalize the monodromy method used in the context of AdS/CFT to theories with BMS symmetry. On the bulk side we consider geodesic Feynman diagrams, recently introduced in [arXiv:1712.07131], evaluated in locally flat geometries generated by backreaction of heavy BMS primary operators. We comment on the implications of these results for the eigenstate thermalization hypothesis in flat holography.