We review the role that infinite-dimensional symmetries arising at the boundary of
asymptotically flat spacetimes play in the context of the celestial holography program. Once …

Gravity in 4 d asymptotically flat spacetime constitutes the archetypal example of a
gravitational system with leaky boundary conditions. Pursuing our previous analysis of …

A bstract The isomorphism between the (extended) BMS 4 algebra and the 1+ 2D Carrollian
conformal algebra hints towards a co-dimension one formalism of flat holography with the …

We show that the asymptotic symmetries close to nonextremal black hole horizons are
generated by an extension of supertranslations. This group is generated by a semidirect …

A bstract Carrollian conformal field theories (carrollian CFTs) are natural field theories on
null infinity of an asymptotically flat spacetime or, more generally, geometries with conformal …

This thesis presents the state of the art in the study of Bondi-Metzner-Sachs (BMS) symmetry
and its applications in the simplified setting of three dimensions. It focuses on presenting all …

A bstract The constrained Hamiltonian analysis of geometric actions is worked out before
applying the construction to the extended Bondi-Metzner-Sachs group in four dimensions …

These notes are a transcript of lectures given by the author in the XVIII Modave summer
school in mathematical physics. The introduction is devoted to a detailed review of the …

Three-dimensional Einstein gravity with a negative cosmological constant admits stationary
black holes that are not necessarily spherically symmetric. We propose boundary conditions …

A bstract The Poincaré invariant vacuum is not unique in quantum gravity. The BMS
supertranslation symmetry originally defined at null infinity is spontaneously broken and …