Gravitational wave polarizations in nonminimally coupled gravity

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Varela, MB (Author) Other; Bertolami, O (Author) FCUP

Journal

Title: Physical Review D: Particles and fields

Vol. 111

ISSN: 0556-2821

Publisher: American Physical Society

Indexing

ISI Web of Knowledge - 1 Citation

Scopus - 1 Citation

Other information

Authenticus ID: P-017-SF9

DOI: 10.1103/physrevd.111.024014

Abstract (EN): The properties of metric perturbations are determined in the context of an expanding Universe governed by a modified theory of gravity with a nonminimal coupling between curvature and matter. We analyze the dynamics of the 6 components of a general helicity decomposition of the metric and stress-energy perturbations, consisting of scalar, vector and tensor sectors. The tensor polarizations are shown to still propagate luminally, in agreement with recent data from gravitational interferometry experiments, while their magnitude decays with an additional factor sourced by the nonminimal coupling. We show that the production of these modes is associated with a modified quadrupole formula at leading order. The vector perturbations still exhibit no radiative behavior, although their temporal evolution is found to be modified, with spatial dependence remaining unaffected. We establish that the scalar perturbations can no longer be treated as identical. We investigate the scalar sector by writing the modified model as an equivalent two- field scalar-tensor theory and find the same scalar degrees of freedom as in previous literature. The different sectors are paired with the corresponding polarization modes, which can be observationally measured by their effects on the relative motion of test particles, thus providing the possibility of testing the modified theory and constraining its parameters.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 23