## Mathematical and Theoretical Physics Seminar: Brown-York charges at null boundaries

- Event Type
- Seminar/Symposium
- Sponsor
- The Physics Department & The Math Department
- Location
- 276 Loomis Laboratory
- Date
- Oct 14, 2021 1:00 pm
- Speaker
- Antony Speranza, UIUC
- Contact
- Stephen Bullwinkel
- bullwink@illinois.edu
- Phone
- 217-333-1652
- Views
- 12
- Originating Calendar
- Physics - Mathematical and Theoretical Physics Seminar
The Brown-York stress tensor provides a means for defining quasilocal gravitational charges in subregions bounded by a timelike hypersurface. I will discuss the generalization of this stress tensor to null hypersurfaces. Such a stress tensor can be derived from the on-shell subregion action of general relativity associated with a Dirichlet variational principle, which fixes an induced Carroll structure on the null boundary. The stress tensor can be shown to satisfy a covariant conservation equation as a result of the gravitational constraint equations on the null surface. For transformations that act covariantly on the null boundary, the Brown-York charges coincide with canonical charges constructed from the Wald-Zoupas procedure, while for anomalous transformations, the charges differ by an intrinsic functional of the boundary geometry. I will comment on some possible applications of the null Brown-York stress tensor to symmetries of asymptotically flat spacetimes and celestial holography.