## “School of Physic”

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Paper   IPM / Physic / 17066
School of Physics
Title:   Null boundary phase space: slicings, news & memory
Author(s):
 1 H. Adami 2 D. Grumiller 3 M.M. Sheikh-Jabbari 4 V. Taghiloo 5 H. Yavartanoo
Status:   Published
Journal: JHEP
Vol.:  11
Year:  2021
Pages:   155
Supported by:  IPM
Abstract:
We construct the boundary phase space in $D$-dimensional Einstein gravity with a generic given co-dimension one null surface ${\cal N}$ as the boundary. The associated boundary symmetry algebra is a semi-direct sum of diffeomorphisms of $\cal N$ and Weyl rescalings. It is generated by $D$ towers of surface charges that are generic functions over $\cal N$. These surface charges can be rendered integrable for appropriate slicings of the phase space, provided there is no graviton flux through $\cal N$. In one particular slicing of this type, the charge algebra is the direct sum of the Heisenberg algebra and diffeomorphisms of the transverse space, ${\cal N}_v$ for any fixed value of the advanced time $v$. Finally, we introduce null surface expansion- and spin-memories, and discuss associated memory effects that encode the passage of gravitational waves through $\cal N$, imprinted in a change of the surface charges.