# Asymptotic structure and the characterisation of gravitational

### APA

Senovilla, J. (2023). Asymptotic structure and the characterisation of gravitational . Perimeter Institute. https://pirsa.org/23090095

### MLA

Senovilla, Jose. Asymptotic structure and the characterisation of gravitational . Perimeter Institute, Sep. 14, 2023, https://pirsa.org/23090095

### BibTex

@misc{ pirsa_PIRSA:23090095, doi = {10.48660/23090095}, url = {https://pirsa.org/23090095}, author = {Senovilla, Jose}, keywords = {Quantum Gravity}, language = {en}, title = {Asymptotic structure and the characterisation of gravitational }, publisher = {Perimeter Institute}, year = {2023}, month = {sep}, note = {PIRSA:23090095 see, \url{https://pirsa.org}} }

Jose Senovilla University of the Basque Country

## Abstract

With the main purpose of identifying the existence of gravitational radiation at infinity (scri), a novel approach to the asymptotic structure of spacetime is presented, focusing mainly in cases with non-negative cosmological constant. The basic idea is to consider the strength of tidal forces experienced by scri. To that end I will introduce the asymptotic (radiant) super-momentum, a causal vector defined at scri with remarkable properties that, in particular, provides an innovative characterization of gravitational radiation valid for the general case with Λ ≥ 0 (and which has been proven to be equivalent when Λ = 0 to the standard one based on the News tensor). This analysis is also shown to be supported by the initial- (or final-) value Cauchy-type problem defined at scri. The implications are discussed in some detail. The geometric structure of scri, and of its cuts, is clarified. The question of whether or not a News tensor can be defined in the presence of a positive cosmological constant is addressed. Several definitions of asymptotic symmetries are presented. Conserved charges that may detect gravitational radiation are exhibited. Balance laws that might be useful as diagnostic tools to test the accuracy of model waveforms discussed. An interpretation of the Geroch `rho' tensor is found. The whole thing will be complemented with a series of illustrative examples based on exact solutions. In particular we will see that exact solutions with black holes will be radiative if, and only if, they are accelerated.

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