Gravitational Waves from Inflation

MYLOVA, MARIA

doi:10.23889/SUthesis.56907

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Gravitational Waves from Inflation / MARIA MYLOVA

Swansea University Author: MARIA MYLOVA

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Copyright: The author, Maria Mylova, 2020.
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DOI (Published version): 10.23889/SUthesis.56907

Abstract

The focus of this work is on the topic of gravitational wave cosmology. We look for new observational signatures for primordial gravitational waves and especially for frameworks that can produce an enhanced tensor spectrum. In such cases, the gravitational wave energy density can enter within the se...

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Published:	Swansea 2020
Institution:	Swansea University
Degree level:	Doctoral
Degree name:	Ph.D
Supervisor:	Tasinato, Gianmassimo
URI:	https://cronfa.swan.ac.uk/Record/cronfa56907
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first_indexed	2021-05-18T16:10:27Z
last_indexed	2021-05-19T03:12:15Z
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spelling	2021-05-18T17:31:55.5863107 v2 56907 2021-05-18 Gravitational Waves from Inflation 63501dab4ebf7e9d3d6e552279fbd97c MARIA MYLOVA MARIA MYLOVA true false 2021-05-18 The focus of this work is on the topic of gravitational wave cosmology. We look for new observational signatures for primordial gravitational waves and especially for frameworks that can produce an enhanced tensor spectrum. In such cases, the gravitational wave energy density can enter within the sensitivity curves of gravi-tational wave detectors or it could leave a measurable imprint in the polarization pattern of the Cosmic Microwave Background radiation. This is very important as more sensitive, next generation experiments are expected to make indirect and direct measurements of the primordial stochastic gravitational wave background.Our investigation showed that an enhanced tensor amplitude can be achieved, within the framework of the Horndeski theory, if there is a short period where slow-roll inﬂation is violated. We considered a model of kinetically driven inﬂation where for a short time the scalar ﬁeld velocity is heavily time-dependent. During that time the would-be decaying tensor mode becomes a growing mode. Analysis of the bispectrum showed that this can lead to sizeable tensor non-Gaussianities.We also considered possible realizations of the eﬀective ﬁeld theory of Scalar-Tensor gravity. In particular, we looked for a setup up of operators that could lead to the enhancement of parity violating eﬀects for tensors. We introduced modiﬁcations to gravity which enabled us to parametrically approach the scale at which maximal parity violation occurs. Using the mathematical machinery for eﬀective ﬁeld theories we showed that sub-leading quadratic operators can become important signalling the presence of the Chern Simons instability. This inevitably implies the existence of non-trivial cubic interactions which could stand the theory strongly coupled at energies not far above the energy scale of inﬂation. Consequently, this can lead to large parity violation in tensor non-Gaussianity. E-Thesis Swansea gravitational waves, inflation, parity violation, non-attractor, non-Gaussianity 21 5 2020 2020-05-21 10.23889/SUthesis.56907 ORCiD identifier https://orcid.org/0000-0003-1772-7014 COLLEGE NANME COLLEGE CODE Swansea University Tasinato, Gianmassimo Doctoral Ph.D STFC, Grant number: DTP ST/N504464/1 2021-05-18T17:31:55.5863107 2021-05-18T17:03:14.6321324 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics MARIA MYLOVA 1 56907__19933__cf819249aefe4c9c9056aece4604a445.pdf Mylova_MariaPhD_Thesis_Final_Redacted_Signature.pdf 2021-05-18T17:25:06.8962053 Output 13312675 application/pdf E-Thesis – open access true Copyright: The author, Maria Mylova, 2020. true eng
title	Gravitational Waves from Inflation
spellingShingle	Gravitational Waves from Inflation MARIA MYLOVA
title_short	Gravitational Waves from Inflation
title_full	Gravitational Waves from Inflation
title_fullStr	Gravitational Waves from Inflation
title_full_unstemmed	Gravitational Waves from Inflation
title_sort	Gravitational Waves from Inflation
author_id_str_mv	63501dab4ebf7e9d3d6e552279fbd97c
author_id_fullname_str_mv	63501dab4ebf7e9d3d6e552279fbd97c_***_MARIA MYLOVA
author	MARIA MYLOVA
author2	MARIA MYLOVA
format	E-Thesis
publishDate	2020
institution	Swansea University
doi_str_mv	10.23889/SUthesis.56907
college_str	Faculty of Science and Engineering
hierarchytype
hierarchy_top_id	facultyofscienceandengineering
hierarchy_top_title	Faculty of Science and Engineering
hierarchy_parent_id	facultyofscienceandengineering
hierarchy_parent_title	Faculty of Science and Engineering
department_str	School of Biosciences, Geography and Physics - Physics{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Physics
document_store_str	1
active_str	0
description	The focus of this work is on the topic of gravitational wave cosmology. We look for new observational signatures for primordial gravitational waves and especially for frameworks that can produce an enhanced tensor spectrum. In such cases, the gravitational wave energy density can enter within the sensitivity curves of gravi-tational wave detectors or it could leave a measurable imprint in the polarization pattern of the Cosmic Microwave Background radiation. This is very important as more sensitive, next generation experiments are expected to make indirect and direct measurements of the primordial stochastic gravitational wave background.Our investigation showed that an enhanced tensor amplitude can be achieved, within the framework of the Horndeski theory, if there is a short period where slow-roll inﬂation is violated. We considered a model of kinetically driven inﬂation where for a short time the scalar ﬁeld velocity is heavily time-dependent. During that time the would-be decaying tensor mode becomes a growing mode. Analysis of the bispectrum showed that this can lead to sizeable tensor non-Gaussianities.We also considered possible realizations of the eﬀective ﬁeld theory of Scalar-Tensor gravity. In particular, we looked for a setup up of operators that could lead to the enhancement of parity violating eﬀects for tensors. We introduced modiﬁcations to gravity which enabled us to parametrically approach the scale at which maximal parity violation occurs. Using the mathematical machinery for eﬀective ﬁeld theories we showed that sub-leading quadratic operators can become important signalling the presence of the Chern Simons instability. This inevitably implies the existence of non-trivial cubic interactions which could stand the theory strongly coupled at energies not far above the energy scale of inﬂation. Consequently, this can lead to large parity violation in tensor non-Gaussianity.
published_date	2020-05-21T04:12:13Z
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score	11.014291

Gravitational Waves from Inflation / MARIA MYLOVA

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