Multipole moments do not uniquely characterize spacetimes beyond general relativity

Fuente: arXiv
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Autori principali: Suvorov, Arthur G., Pappas, George
Natura: Preprint
Pubblicazione: 2025
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author Suvorov, Arthur G.
Pappas, George
author_facet Suvorov, Arthur G.
Pappas, George
contents Spacetimes in general relativity can be uniquely decomposed into a set of multipole moments. Given the usefulness of moments in the categorization of radiation patterns, tidal deformations, and other phenomena associated with compact objects, a number of studies have explored their construction in beyond-Einstein theories of gravity. It is shown here that uniqueness does not necessarily extend across theories: by comparing a few static and spherically-symmetric solutions in different theories, we find that two distinct objects can possess the same Geroch-Hansen moments. Moreover, two metrics can match and yet take different moments. Implications of this result are explored in the context of black-hole shadows and ``universal'' relations hinging on moment computations.
format Preprint
id arxiv_https___arxiv_org_abs_2511_22405
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Multipole moments do not uniquely characterize spacetimes beyond general relativity
Suvorov, Arthur G.
Pappas, George
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
High Energy Physics - Theory
Spacetimes in general relativity can be uniquely decomposed into a set of multipole moments. Given the usefulness of moments in the categorization of radiation patterns, tidal deformations, and other phenomena associated with compact objects, a number of studies have explored their construction in beyond-Einstein theories of gravity. It is shown here that uniqueness does not necessarily extend across theories: by comparing a few static and spherically-symmetric solutions in different theories, we find that two distinct objects can possess the same Geroch-Hansen moments. Moreover, two metrics can match and yet take different moments. Implications of this result are explored in the context of black-hole shadows and ``universal'' relations hinging on moment computations.
title Multipole moments do not uniquely characterize spacetimes beyond general relativity
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
High Energy Physics - Theory
url https://arxiv.org/abs/2511.22405