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Quantum propagation and initial value problems in curved space. / Ross James Stanley

Swansea University Author: Ross James Stanley

Abstract

Quantum field theory is studied within the semi-classical gravity approximation. The quantum correction to the propagation of both photons and gravitons in a general curved space background is calculated showing a non-trivial spacetime refractive index as well as a dynamical dressing (or undressing)...

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Published: 2012
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42356
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last_indexed 2018-08-03T10:09:56Z
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spelling 2018-08-02T16:24:28.9478019 v2 42356 2018-08-02 Quantum propagation and initial value problems in curved space. e73443cab52b51caf3c4e16c94a27e42 NULL Ross James Stanley Ross James Stanley true true 2018-08-02 Quantum field theory is studied within the semi-classical gravity approximation. The quantum correction to the propagation of both photons and gravitons in a general curved space background is calculated showing a non-trivial spacetime refractive index as well as a dynamical dressing (or undressing) of the particle state. The initial interacting particle's 'dressing', the cloud of virtual particles that surrounds it, may receive corrections from an infinite number of modes even for flat space. When gravitational tidal effects remove this dressing, squeezing it back into the bare particle, this leads to an amplification in a way consistent with unitarity. There is a possible shift discovered in the graviton wavefront velocity related to higher order curvature couplings, although in this calculation there is also a logarithmic divergence at high frequencies, leading to a breakdown of the perturbative approximation. Next we consider initial value problems and the stability of de Sitter space. Here the self decay of a massive scalar in de Sitter space is proposed to lead to a particle explosion where divergent growth of the field expectation value is observed. Directly investigating this divergent field expectation value a one loop calculation is completed for a massive scalar particle in 3-dimensional de Sitter space. This result has characteristic secular growth that can be summed into a rapidly decaying exponential by using the dynamical renormalisation group. Finally the evolution of two point functions is studied, by numerically solving their equations of motion using the Kaydanoff-Baym equations in 2-dimensional de Sitter space. Here we see a decay of the vacuum state due to the coupling. This appears to be related to the choice of initial conditions be chosen to match the free field vacuum plus non-interacting particles. This choice is made inappropriate by the dynamical dressing of the bare particle states. E-Thesis Theoretical physics.;Quantum physics. 31 12 2012 2012-12-31 COLLEGE NANME Physics COLLEGE CODE Swansea University Doctoral Ph.D 2018-08-02T16:24:28.9478019 2018-08-02T16:24:28.9478019 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics Ross James Stanley NULL 1 0042356-02082018162448.pdf 10798064.pdf 2018-08-02T16:24:48.0100000 Output 3957263 application/pdf E-Thesis true 2018-08-02T16:24:48.0100000 false
title Quantum propagation and initial value problems in curved space.
spellingShingle Quantum propagation and initial value problems in curved space.
Ross James Stanley
title_short Quantum propagation and initial value problems in curved space.
title_full Quantum propagation and initial value problems in curved space.
title_fullStr Quantum propagation and initial value problems in curved space.
title_full_unstemmed Quantum propagation and initial value problems in curved space.
title_sort Quantum propagation and initial value problems in curved space.
author_id_str_mv e73443cab52b51caf3c4e16c94a27e42
author_id_fullname_str_mv e73443cab52b51caf3c4e16c94a27e42_***_Ross James Stanley
author Ross James Stanley
author2 Ross James Stanley
format E-Thesis
publishDate 2012
institution Swansea University
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 Quantum field theory is studied within the semi-classical gravity approximation. The quantum correction to the propagation of both photons and gravitons in a general curved space background is calculated showing a non-trivial spacetime refractive index as well as a dynamical dressing (or undressing) of the particle state. The initial interacting particle's 'dressing', the cloud of virtual particles that surrounds it, may receive corrections from an infinite number of modes even for flat space. When gravitational tidal effects remove this dressing, squeezing it back into the bare particle, this leads to an amplification in a way consistent with unitarity. There is a possible shift discovered in the graviton wavefront velocity related to higher order curvature couplings, although in this calculation there is also a logarithmic divergence at high frequencies, leading to a breakdown of the perturbative approximation. Next we consider initial value problems and the stability of de Sitter space. Here the self decay of a massive scalar in de Sitter space is proposed to lead to a particle explosion where divergent growth of the field expectation value is observed. Directly investigating this divergent field expectation value a one loop calculation is completed for a massive scalar particle in 3-dimensional de Sitter space. This result has characteristic secular growth that can be summed into a rapidly decaying exponential by using the dynamical renormalisation group. Finally the evolution of two point functions is studied, by numerically solving their equations of motion using the Kaydanoff-Baym equations in 2-dimensional de Sitter space. Here we see a decay of the vacuum state due to the coupling. This appears to be related to the choice of initial conditions be chosen to match the free field vacuum plus non-interacting particles. This choice is made inappropriate by the dynamical dressing of the bare particle states.
published_date 2012-12-31T03:52:48Z
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score 11.016235

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