# Black Hole Entropy from BMS Symmetry at the Horizon

## TL;DR

This paper explores how enhanced BMS symmetries at a black hole horizon can be used to derive the black hole entropy, providing a symmetry-based understanding of this fundamental property.

## Contribution

It demonstrates that horizon-preserving diffeomorphisms form a BMS${}_3$ algebra that can determine black hole entropy, linking horizon symmetries to thermodynamic properties.

## Key findings

- BMS${}_3$ symmetry at the horizon is enhanced compared to generic diffeomorphisms.
- The augmented symmetry algebra can be used to compute black hole entropy.
- Dimensional reduction and covariant phase space methods are effective tools in this analysis.

## Abstract

Near the horizon, the obvious symmetries of a black hole spacetime---the horizon-preserving diffeomorphisms---are enhanced to a larger symmetry group with a BMS${}_3$ algebra. Using dimensional reduction and covariant phase space techniques, I investigate this augmented symmetry, and show that it is strong enough to determine the black hole entropy.