Bilinear products and the orthogonality of quasinormal modes on hyperboloidal foliations

Fuente: arXiv
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Autori principali: Minucci, Marica, Macedo, Rodrigo Panosso, Pantelidou, Christiana, Sberna, Laura
Natura: Preprint
Pubblicazione: 2026
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author Minucci, Marica
Macedo, Rodrigo Panosso
Pantelidou, Christiana
Sberna, Laura
author_facet Minucci, Marica
Macedo, Rodrigo Panosso
Pantelidou, Christiana
Sberna, Laura
contents We explore the properties of bilinear products for black-hole quasinormal modes (QNMs) formulated on hyperboloidal foliations. We find that, although QNM solutions are smooth and finite on future-directed hyperboloids, the integrand of the bilinear form with respect to which the modes are orthogonal is still divergent. This is a result of the reflection (equivalently, CPT) transformation required in the definition of the products, which modifies the behaviour of the integrand at the boundaries. We present several regularisation procedures that yield a finite and well-defined bilinear form. In addition, we examine an alternative definition of the bilinear products that incorporates flux contributions, discussing its advantages and limitations. Finally, we define the QNM excitation factors and coefficients within the hyperboloidal framework in terms of the bilinear products, and compute them explicitly for a choice of mode numbers and constant initial data. For concreteness, we work with the QNMs associated to scalar perturbations of the Schwarzschild family of spacetimes.
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id arxiv_https___arxiv_org_abs_2604_13182
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Bilinear products and the orthogonality of quasinormal modes on hyperboloidal foliations
Minucci, Marica
Macedo, Rodrigo Panosso
Pantelidou, Christiana
Sberna, Laura
General Relativity and Quantum Cosmology
Mathematical Physics
We explore the properties of bilinear products for black-hole quasinormal modes (QNMs) formulated on hyperboloidal foliations. We find that, although QNM solutions are smooth and finite on future-directed hyperboloids, the integrand of the bilinear form with respect to which the modes are orthogonal is still divergent. This is a result of the reflection (equivalently, CPT) transformation required in the definition of the products, which modifies the behaviour of the integrand at the boundaries. We present several regularisation procedures that yield a finite and well-defined bilinear form. In addition, we examine an alternative definition of the bilinear products that incorporates flux contributions, discussing its advantages and limitations. Finally, we define the QNM excitation factors and coefficients within the hyperboloidal framework in terms of the bilinear products, and compute them explicitly for a choice of mode numbers and constant initial data. For concreteness, we work with the QNMs associated to scalar perturbations of the Schwarzschild family of spacetimes.
title Bilinear products and the orthogonality of quasinormal modes on hyperboloidal foliations
topic General Relativity and Quantum Cosmology
Mathematical Physics
url https://arxiv.org/abs/2604.13182