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The rise of the primordial tensor spectrum from an early scalar-tensor epoch

Debika Chowdhury, Gianmassimo Tasinato Orcid Logo, Ivonne Zavala Carrasco Orcid Logo

Journal of Cosmology and Astroparticle Physics, Volume: 2022, Issue: 08, Start page: 010

Swansea University Authors: Debika Chowdhury, Gianmassimo Tasinato Orcid Logo, Ivonne Zavala Carrasco Orcid Logo

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Abstract

Primordial gravitational waves (PGW) produced during inflation span a large range of frequencies, carrying information on the dynamics of the primordial universe. During an early scalar-tensor dominated epoch, the amplitude of the PGW spectrum can be enhanced over a wide range of frequencies. To stu...

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Published in: Journal of Cosmology and Astroparticle Physics
ISSN: 1475-7516
Published: IOP Publishing 2022
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa60779
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Abstract: Primordial gravitational waves (PGW) produced during inflation span a large range of frequencies, carrying information on the dynamics of the primordial universe. During an early scalar-tensor dominated epoch, the amplitude of the PGW spectrum can be enhanced over a wide range of frequencies. To study this phenomenon, we focus on a class of scalar-tensor theories, well motivated by high energy theories of dark energy and dark matter, where the scalar is conformally and disformally coupled to matter during the early cosmological evolution. For a conformally dominated epoch, the PGW spectrum has a flat step-like shape. More interestingly, a disformally dominated epoch is characterised by a peaked spectrum with a broken power-law profile, with slopes depending on the scalar-tensor theory considered. We introduce a graphical tool, called broken power-law sensitivity curve, as a convenient visual indicator for understanding whether a given broken power-law profile can be detected by GW experiments. We then analyse the GW spectra for a variety of representative conformal and disformal models, discussing their detectability prospects with the Einstein Telescope (ET), Laser Interferometer Space Antenna (LISA), DECi-hertz Interferometer Gravitational wave Observatory (DECIGO), and Big Bang Observer (BBO).
Keywords: Gravitational waves in GR and beyond: theory, physics of the early universe, primordial gravitational waves (theory), gravitational waves / theory
College: Faculty of Science and Engineering
Funders: D. C. acknowledges the support of the Supercomputing Wales project, which is part-funded by the European Regional Development Fund (ERDF) via Welsh Government. D. C. would also like to thank H. V. Ragavendra for discussions. This work is part-funded by the STFC grant ST/T000813/1.
Issue: 08
Start Page: 010