# Loop corrected subleading soft graviton theorem from anomalous BRST Ward identity

### APA

Wetzstein, T. (2024). Loop corrected subleading soft graviton theorem from anomalous BRST Ward identity . Perimeter Institute. https://pirsa.org/24030114

### MLA

Wetzstein, Tom. Loop corrected subleading soft graviton theorem from anomalous BRST Ward identity . Perimeter Institute, Mar. 14, 2024, https://pirsa.org/24030114

### BibTex

@misc{ pirsa_PIRSA:24030114, doi = {10.48660/24030114}, url = {https://pirsa.org/24030114}, author = {Wetzstein, Tom}, keywords = {Quantum Gravity}, language = {en}, title = {Loop corrected subleading soft graviton theorem from anomalous BRST Ward identity }, publisher = {Perimeter Institute}, year = {2024}, month = {mar}, note = {PIRSA:24030114 see, \url{https://pirsa.org}} }

Tom Wetzstein Laboratory of Theoretical and High Energy Physics

## Abstract

Extended BMS symmetry is believed to be a fundamental symmetry of any classical gravitational scattering process, as well as of the quantum gravity S-matrix. We explore this property using the BRST formulation of BMS symmetry, which allows to construct a non trivial solution of the Wess-Zumino consistency condition at the null boundaries of spacetime. We interpret this solution as an anomaly for asymptotic BRST Ward identities for superrotations. By relating them to the leading and subleading soft graviton theorem, we recover the well known results that the leading soft theorem is exact at all loop in perturbation theory without ever referring to Feynman diagrams, while the anomaly for superrotations is at the origin of the 1-loop correction to the subleading soft factor. This construction provides a rigorous, fully quantum origin for the invariance of the S-matrix under asymptotic symmetries.

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