Generalized perturbations in modified gravity and dark energy PDF
Preview Generalized perturbations in modified gravity and dark energy
Springer Theses Recognizing Outstanding Ph.D. Research Jonathan Pearson Generalized Perturbations in Modified Gravity and Dark Energy Springer Theses Recognizing Outstanding Ph.D. Research For furthervolumes: http://www.springer.com/series/8790 Aims and Scope The series ‘‘Springer Theses’’ brings together a selection of the very best Ph.D. theses from around the world and across the physical sciences. Nominated and endorsed by two recognized specialists, each published volume has been selected for its scientific excellence and the high impact of its contents for the pertinent fieldofresearch.Forgreateraccessibilitytonon-specialists,thepublishedversions includeanextendedintroduction,aswellasaforewordbythestudent’ssupervisor explaining the special relevance of the work for the field. 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Jonathan Pearson Generalized Perturbations in Modified Gravity and Dark Energy Doctoral Thesis accepted by the University of Manchester, UK 123 Author Supervisor Dr. Jonathan Pearson Prof.Richard Battye Department of Mathematical Sciences School ofPhysicsand Astronomy Durham University Universityof Manchester Durham Manchester UK UK ISSN 2190-5053 ISSN 2190-5061 (electronic) ISBN 978-3-319-01209-4 ISBN 978-3-319-01210-0 (eBook) DOI 10.1007/978-3-319-01210-0 SpringerChamHeidelbergNewYorkDordrechtLondon LibraryofCongressControlNumber:2013942999 (cid:2)SpringerInternationalPublishingSwitzerland2014 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodology now known or hereafter developed. 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While the advice and information in this book are believed to be true and accurate at the date of publication,neithertheauthorsnortheeditorsnorthepublishercanacceptanylegalresponsibilityfor anyerrorsoromissionsthatmaybemade.Thepublishermakesnowarranty,expressorimplied,with respecttothematerialcontainedherein. Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Publications The work in this thesis is partly based upon the following publications: • Massive gravity, the elasticity of space-time, and perturbations in the dark sector [259], with Richard Battye • Effective action approach to cosmological perturbations in dark energy and modified gravity [187], published in JCAP with Richard Battye. • Effective field theory for perturbations in dark energy and modified gravity [216], conference proceedings. • Equations of state for dark sector perturbations for general high derivative scalar-tensor theories: in preparation with Richard Battye. • Parameterizing dark sector perturbations via equations of state: in preparation with Richard Battye • Observational signatures and constraints on generalized cosmological pertur- bations: in preparation with Richard Battye and Adam Moss. That there exist rules to be checked at all is some sort of miracle —Richard Feynman Book-keeping, continued to all eternity, could not produce one farthing —C. S. Lewis The creator does not appear in the scientific account, but it is clearly ridiculous to deduce from this that the creator did not exist —John Lennox In the beginning God created the heavens and the earth. Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters —Genesis 1 To my parents, Marcus, and Anna Supervisor’s Foreword TheNobelPrizeforPhysicsin2011wasawardedjointlytoSaulPerlmutter,Adam Reiss, and Brian Schmidt for the discovery of cosmic acceleration. However, its origin is still one of the greatest mysteries in modern physics. A cosmological constantis,perhaps,thesimplestexplanationbutitisdifficulttoreconcilewithour understanding of modern particle physics theories that predicts a vacuum energy 120 orders of magnitude larger than observed. It has been suggested that a dynamical component ofthe Universe, knownasdark energy,ormodificationsto Einstein’s theory of General Relativity in the infrared could be responsible. There are now many theories that have been proposed to describe dark energy and modified gravity. Observations are likely to play a key role in distinguishing thedifferenttheories.Therearetwoclassesofobservations:(i)thosethatareonly sensitive to the background evolution; (ii) those that are, in addition, sensitive to theevolutionofperturbations. Inparticular,weakgravitational lensingisaffected bythedistributionofthedarkenergy,ortheevolutionofperturbationsinmodified gravity. The observed distortions of galaxy shapes, or those observed in the Cosmic Microwave Background, can be very different to those predicted for models involving a cosmological constant. The goal of this thesis was to develop a general formalism for modeling the evolutionofperturbationsindarkenergyandmodifiedgravity.Thebasicideawas to try to make as few theoretical assumptions as possible in deriving the obser- vational predictions. The hope would then be that those analyzing observations wouldmeasurethefreeparametersinthemodelandallowustohoneinthecorrect theory. Starting from the field content of a model and some basic arguments of sym- metry, Jonathan was able to derive expressions for the effective fluid variables in terms of the active degrees offreedom of whatever is causing the cosmic accel- eration. In a number of cases, it was possible to eliminate the internal degrees of freedomanddeduceanequationofstatefortheperturbationsthatisparameterized xi xii Supervisor’sForeword byanumberoffreefunctionsoftime.Hethenwentontoperformasurveyofthe possible observational consequences. In work done since the submission of the thesis,wehaveextendedthebasicideatoawiderclassofmodelsand,atpresent, we are investigating the constraints imposed from the recently released data from the Planck satellite. Manchester, June 2013 Prof. Richard Battye
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