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arXiv · 2504.10304

Extended-BMS Anomalies and Flat Space Holography

Laurent Baulieu·Luca Ciambelli·Tom Wetzstein
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Abstract

We geometrically determine the BRST symmetry of a three-dimensional extended BMS field theory defined at the null boundary of asymptotically flat four-dimensional spaces. We then discuss its ghost number zero and one cocycles, independently of the four-dimensional bulk. The former determine a topological Lagrangian localized on the boundary of null infinity, while the latter classify the corresponding anomalies. This classification reproduces the eBMS anomalies known from the bulk, providing a rare non-perturbative test of flat space holography. While supertranslations are anomaly-free, superrotations admit independent central charges. This theory can thus be dual to Einstein gravity only if these central charges are dictated by the bulk.

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Laurent Baulieu, Luca Ciambelli, Tom Wetzstein. 2026-08-27. Extended-BMS Anomalies and Flat Space Holography. https://arxiv.org/abs/2504.10304

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