# Black Hole Entropy from BMS Symmetry at the Horizon

### APA

Carlip, S. (2017). Black Hole Entropy from BMS Symmetry at the Horizon. Perimeter Institute. https://pirsa.org/17070031

### MLA

Carlip, Steve. Black Hole Entropy from BMS Symmetry at the Horizon. Perimeter Institute, Jul. 17, 2017, https://pirsa.org/17070031

### BibTex

@misc{ pirsa_PIRSA:17070031, doi = {10.48660/17070031}, url = {https://pirsa.org/17070031}, author = {Carlip, Steve}, keywords = {Other}, language = {en}, title = {Black Hole Entropy from BMS Symmetry at the Horizon}, publisher = {Perimeter Institute}, year = {2017}, month = {jul}, note = {PIRSA:17070031 see, \url{https://pirsa.org}} }

Steve Carlip University of California, Davis

## Abstract

One of the basic puzzles of black hole thermodynamics is the simplicity and universality of the Bekenstein-Hawking entropy. The idea that this entropy might be governed by a symmetry at the horizon is an old one, but until now efforts have focused on conformal symmetries, either at infinity or on a "stretched horizon." I argue that a better approach uses a BMS-like symmetry of the horizon itself. This avoids the limitations of previous attempts (including my own), and explains the entropy in terms of a generalization of the Cardy formula for the density of states.