Eur. Phys. J. C (2018) 78: 303
https://doi.org/10.1140/epjc/s10052-018-5781-5

Regular Article - Theoretical Physics

Gravitational waves in theories with a non-minimal curvature-matter coupling

¹ Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto and Centro de Física do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
² Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências da Universidade de Lisboa, Edifício C8, Campo Grande, 1749-016, Lisbon, Portugal

^* e-mail: claudio.gomes@fc.up.pt

Received: 26 February 2018
Accepted: 4 April 2018
Published online: 18 April 2018

Abstract

Gravitational waves in the presence of a non-minimal curvature-matter coupling are analysed, both in the Newman–Penrose and perturbation theory formalisms. Considering a cosmological constant as a source, the non-minimally coupled matter-curvature model reduces to f(R) theories. This is in good agreement with the most recent data. Furthermore, a dark energy-like fluid is briefly considered, where the propagation equation for the tensor modes differs from the previous scenario, in that the scalar mode equation has an extra term, which can be interpreted as the longitudinal mode being the result of the mixture of two fundamental excitations and .