Regular Article - Theoretical Physics
No constraints for f(T) gravity from gravitational waves induced from primordial black hole fluctuations
National Observatory of Athens, Lofos Nymfon, 11852, Athens, Greece
2 Department of Physics, National and Kapodistrian University of Athens, Zografou Campus GR, 157 73, Athens, Greece
3 Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, 11527, Athens, Greece
4 School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516, Nicosia, Cyprus
5 CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, 230026, Hefei, Anhui, People’s Republic of China
6 Departamento de Matemáticas, Universidad Católica del Norte, Avda. Angamos 0610, 1280, Casilla, Antofagasta, Chile
Accepted: 22 December 2022
Published online: 17 January 2023
Primordial black hole (PBH) fluctuations can induce a stochastic gravitational wave background at second order, and since this procedure is sensitive to the underlying gravitational theory it can be used as a novel tool to test general relativity and extract constraints on possible modified gravity deviations. We apply this formalism in the framework of f(T) gravity, considering three viable mono-parametric models. In particular, we investigate the induced modifications at the level of the gravitational-wave source, which is encoded in terms of the power spectrum of the PBH gravitational potential, as well as at the level of their propagation, described in terms of the Green function which quantifies the propagator of the tensor perturbations. We find that, within the observationally allowed range of the f(T) model-parameters, the obtained deviations from general relativity, both at the levels of source and propagation, are practically negligible. Hence, we conclude that realistic and viable f(T) theories can safely pass the primordial black hole constraints, which may offer an additional argument in their favor.
© The Author(s) 2023
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