Speaker:	Gabriel Arenas-Henriquez (Yau Center, Tsinghua)
Title:	Two Routes to Flat Space Holography
Date (JST):	Tue, Dec 02, 2025, 13:30 - 15:00
Place:	Seminar Room A
Related File:	3475.pdf
Abstract:	I will discuss recent developments on two complementary approaches to flat holography, particularly in the context of the flat/Carrollian CFT (flat/CCFT) correspondence. In the first part, I will focus on the bulk perspective of the duality by considering asymptotically AdS spacetimes in four dimensions and their flat limit. I will introduce a criterion for the presence or absence of gravitational radiation, which can be reformulated as a sufficient condition encoded in a radiative vector. The radiative content of the bulk is captured by the boundary Cotton tensor and stress tensor, which we reinterpret holographically in terms of fluid variables in the dual boundary theory. For algebraically special solutions such as Robinson–Trautman and C-metric geometries, we show that dissipative terms in the boundary stress tensor are in one-to-one correspondence with bulk radiation, and that this criterion admits a well-defined flat limit reproducing the standard interpretation of the Bondi news tensor. In particular, the three-dimensional Carrollian fluid at null infinity inherits dissipative effects sourced by radiation in the bulk. In the second part of the talk, I will adopt a bottom-up perspective and consider an explicit Carrollian conformal field theory in two dimensions. I will introduce a two-dimensional interacting fermionic CCFT, which shares similarities with the Thirring model while exhibiting distinct ultra-relativistic features. This theory provides an explicit example of an exactly solvable CCFT at both classical and quantum levels. I will describe the structure of its correlation functions, its connection with the Thirring model, and the computation of its central charges. I will then comment on why this theory does not satisfy the necessary ingredients to serve as a putative dual of flat space. Instead, I will argue that the ultra-relativistic limit must be accompanied by a large-N limit to produce a CCFT with genuinely non-trivial dynamics.

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