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A study of QCD at finite density using complex Langevin dynamics. / FELIPE ATTANASIO

Swansea University Author: FELIPE ATTANASIO

DOI (Published version): 10.23889/SUthesis.57160

Abstract

Numerical simulations are a standard tool to investigate field theories innon-perturbative regimes. Typical algorithms used to evaluate path integralsin Euclidean space rely on importance sampling methods; i.e., aprobabilistic interpretation of the Boltzmann weight eS. However, manytheories of inter...

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Published: Swansea University 2017
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Gert Aarts, Chris Alton
URI: https://cronfa.swan.ac.uk/Record/cronfa57160
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first_indexed 2021-06-17T09:20:27Z
last_indexed 2021-06-19T03:25:36Z
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spelling 2021-06-18T12:36:05.8329090 v2 57160 2021-06-17 A study of QCD at finite density using complex Langevin dynamics. b8f2975115a5c285bf6e6efd314e0eaf FELIPE ATTANASIO FELIPE ATTANASIO true false 2021-06-17 Numerical simulations are a standard tool to investigate field theories innon-perturbative regimes. Typical algorithms used to evaluate path integralsin Euclidean space rely on importance sampling methods; i.e., aprobabilistic interpretation of the Boltzmann weight eS. However, manytheories of interest suffer from the infamous sign problem: the action iscomplex and the Boltzmann weight cannot be used as a probability distribution.Complex Langevin simulations allow numerical studies of theoriesthat exhibit the sign problem, such as QCD at finite density.In this thesis, we study methods to investigate the phase diagram of QCDin the temperature{chemical potential plane, using the complex Langevinmethod. We provide results on the phase diagram for the heavy-denseapproximation of QCD (HDQCD) for three spatial volumes, using complexLangevin and the gauge cooling technique. We also present polynomialfits of the critical temperature as function of the chemical potential foreach volume. Subsequently, we discuss instabilities encountered during thisstudy, which motivated a novel technique, named Dynamic Stabilisation,which will be introduced and the theoretical ideas behind it, explained.Dynamic stabilisation was, then, used in an investigation of the dependencyof the critical chemical potential on the hopping parameter. The two previousstudies were used to guide a second examination of the HDQCD phasediagram, focussed around the phase boundary.Lastly, we present preliminary results on the phase diagram of QCD withfully dynamical quarks at high temperatures. This shows that complexLangevin, augmented with gauge cooling and dynamic stabilisation, is suitedfor investigating QCD at finite chemical potential. E-Thesis Swansea University Langevin simulations, QCD 21 9 2017 2017-09-21 10.23889/SUthesis.57160 COLLEGE NANME COLLEGE CODE Swansea University Gert Aarts, Chris Alton Doctoral Ph.D Science without Borders Not Required Brazil: Science without Borders Scholarship number Bex 9463/13-5. 2021-06-18T12:36:05.8329090 2021-06-17T10:09:52.8723315 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics FELIPE ATTANASIO 1 57160__20183__de526a2c5e254be48969e56bf3bfb79a.pdf Attanasio, Felipe. PhD.thesis.pdf 2021-06-17T10:23:11.5688643 Output 9505610 application/pdf Version of Record true Copyright: The author, Felipe Attanasio, 2017. true eng
title A study of QCD at finite density using complex Langevin dynamics.
spellingShingle A study of QCD at finite density using complex Langevin dynamics.
FELIPE ATTANASIO
title_short A study of QCD at finite density using complex Langevin dynamics.
title_full A study of QCD at finite density using complex Langevin dynamics.
title_fullStr A study of QCD at finite density using complex Langevin dynamics.
title_full_unstemmed A study of QCD at finite density using complex Langevin dynamics.
title_sort A study of QCD at finite density using complex Langevin dynamics.
author_id_str_mv b8f2975115a5c285bf6e6efd314e0eaf
author_id_fullname_str_mv b8f2975115a5c285bf6e6efd314e0eaf_***_FELIPE ATTANASIO
author FELIPE ATTANASIO
author2 FELIPE ATTANASIO
format E-Thesis
publishDate 2017
institution Swansea University
doi_str_mv 10.23889/SUthesis.57160
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 Numerical simulations are a standard tool to investigate field theories innon-perturbative regimes. Typical algorithms used to evaluate path integralsin Euclidean space rely on importance sampling methods; i.e., aprobabilistic interpretation of the Boltzmann weight eS. However, manytheories of interest suffer from the infamous sign problem: the action iscomplex and the Boltzmann weight cannot be used as a probability distribution.Complex Langevin simulations allow numerical studies of theoriesthat exhibit the sign problem, such as QCD at finite density.In this thesis, we study methods to investigate the phase diagram of QCDin the temperature{chemical potential plane, using the complex Langevinmethod. We provide results on the phase diagram for the heavy-denseapproximation of QCD (HDQCD) for three spatial volumes, using complexLangevin and the gauge cooling technique. We also present polynomialfits of the critical temperature as function of the chemical potential foreach volume. Subsequently, we discuss instabilities encountered during thisstudy, which motivated a novel technique, named Dynamic Stabilisation,which will be introduced and the theoretical ideas behind it, explained.Dynamic stabilisation was, then, used in an investigation of the dependencyof the critical chemical potential on the hopping parameter. The two previousstudies were used to guide a second examination of the HDQCD phasediagram, focussed around the phase boundary.Lastly, we present preliminary results on the phase diagram of QCD withfully dynamical quarks at high temperatures. This shows that complexLangevin, augmented with gauge cooling and dynamic stabilisation, is suitedfor investigating QCD at finite chemical potential.
published_date 2017-09-21T04:12:41Z
_version_ 1763753864632205312
score 11.016235

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