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Cosmological implications of spectator and dynamical fields during inflation / JONATHAN HOLLAND

Swansea University Author: JONATHAN HOLLAND

DOI (Published version): 10.23889/SUthesis.56506

Abstract

Some possible cosmological implications of the inclusion of spectator gauge fields in the inflationary action are considered. In this context, a spec-tator field is a field that is not directly responsible for inflation but can affect cosmological observables. Spectator gauge fields can lead to novel and d...

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Published: Swansea 2020
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Zavala, Ivonne; Tasinato, Gianmassimo; Nunez, Carlos
URI: https://cronfa.swan.ac.uk/Record/cronfa56506
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first_indexed 2021-03-23T17:07:57Z
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spelling 2021-03-23T17:26:05.2210702 v2 56506 2021-03-23 Cosmological implications of spectator and dynamical fields during inflation ecc3e28e7cfcab7e463fb4e5f7cebd3a JONATHAN HOLLAND JONATHAN HOLLAND true false 2021-03-23 Some possible cosmological implications of the inclusion of spectator gauge fields in the inflationary action are considered. In this context, a spec-tator field is a field that is not directly responsible for inflation but can affect cosmological observables. Spectator gauge fields can lead to novel and distinguishable features in inflationary models (as compared to single-field inflation) that may be detectable. A model of anisotropic inflation is considered where universal anisotropy is maintained through a vector field that is coupled to both the inflaton and its derivative. The derivative cou-pling reduces the anisotropy induced when compared to the non-derivative case, reducing tension with observations. SU(N) gauge fields appear natu-rally in the actions of string inflation models. The inclusion of an SU(N) gauge field coupled both to scalars and pseudo-scalars (axions) is considered in two models of string inflation whose inflatons are K¨ahler moduli: K¨ahler moduli inflation and fibre inflation. It is shown that the coupling between the axion and the gauge field can lead to a large (chiral) enhancement of the tensor spectrum of these two models. In the case of K¨ahler moduli inflation, a model that generically predicts an unobservable value for the tensor-to-scalar ratio (r  10−3), this enhancement is capable of boost-ing the tensor-to-scalar ratio to values that will be potentially observable at next generation detectors. However, the parameters required to achieve this goal may present a challenge for its successful realisation in string theory. In the case of fibre inflation, a model that generically predicts an observable value for the tensor-to-scalar ratio, it is shown that this enhancement can render the tensor spectrum of fibre inflation almost entirely chiral, giving it a distinguishable feature that may be detectable. E-Thesis Swansea Cosmology, inflation, high energy physics 25 9 2020 2020-09-25 10.23889/SUthesis.56506 COLLEGE NANME COLLEGE CODE Swansea University Zavala, Ivonne; Tasinato, Gianmassimo; Nunez, Carlos Doctoral Ph.D STFC/College of Science 2021-03-23T17:26:05.2210702 2021-03-23T17:06:06.8716786 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics JONATHAN HOLLAND 1 56506__19538__aa2ce0196e514e68b329ee0b6977773a.pdf Holland__Jonathan_PhD_Thesis_Final_2020_Redacted_Signature.pdf 2021-03-23T17:17:06.5892299 Output 11805118 application/pdf E-Thesis – open access true Copyright: The author, Jonathan Holland, 2020. true eng
title Cosmological implications of spectator and dynamical fields during inflation
spellingShingle Cosmological implications of spectator and dynamical fields during inflation
JONATHAN HOLLAND
title_short Cosmological implications of spectator and dynamical fields during inflation
title_full Cosmological implications of spectator and dynamical fields during inflation
title_fullStr Cosmological implications of spectator and dynamical fields during inflation
title_full_unstemmed Cosmological implications of spectator and dynamical fields during inflation
title_sort Cosmological implications of spectator and dynamical fields during inflation
author_id_str_mv ecc3e28e7cfcab7e463fb4e5f7cebd3a
author_id_fullname_str_mv ecc3e28e7cfcab7e463fb4e5f7cebd3a_***_JONATHAN HOLLAND
author JONATHAN HOLLAND
author2 JONATHAN HOLLAND
format E-Thesis
publishDate 2020
institution Swansea University
doi_str_mv 10.23889/SUthesis.56506
college_str Faculty of Science and Engineering
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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 Some possible cosmological implications of the inclusion of spectator gauge fields in the inflationary action are considered. In this context, a spec-tator field is a field that is not directly responsible for inflation but can affect cosmological observables. Spectator gauge fields can lead to novel and distinguishable features in inflationary models (as compared to single-field inflation) that may be detectable. A model of anisotropic inflation is considered where universal anisotropy is maintained through a vector field that is coupled to both the inflaton and its derivative. The derivative cou-pling reduces the anisotropy induced when compared to the non-derivative case, reducing tension with observations. SU(N) gauge fields appear natu-rally in the actions of string inflation models. The inclusion of an SU(N) gauge field coupled both to scalars and pseudo-scalars (axions) is considered in two models of string inflation whose inflatons are K¨ahler moduli: K¨ahler moduli inflation and fibre inflation. It is shown that the coupling between the axion and the gauge field can lead to a large (chiral) enhancement of the tensor spectrum of these two models. In the case of K¨ahler moduli inflation, a model that generically predicts an unobservable value for the tensor-to-scalar ratio (r  10−3), this enhancement is capable of boost-ing the tensor-to-scalar ratio to values that will be potentially observable at next generation detectors. However, the parameters required to achieve this goal may present a challenge for its successful realisation in string theory. In the case of fibre inflation, a model that generically predicts an observable value for the tensor-to-scalar ratio, it is shown that this enhancement can render the tensor spectrum of fibre inflation almost entirely chiral, giving it a distinguishable feature that may be detectable.
published_date 2020-09-25T04:11:31Z
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score 11.014358

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