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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
E-Mail
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.

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