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Please use this identifier to cite or link to this item: http://hdl.handle.net/1843/51529
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dc.contributor.advisor1Marcos Donizeti Rodrigues Sampaiopt_BR
dc.contributor.advisor1Latteshttp://lattes.cnpq.br/9957455292822908pt_BR
dc.contributor.advisor-co1Karen Milena Fonseca Romeropt_BR
dc.contributor.referee1Pablo Lima Saldanhapt_BR
dc.contributor.referee2George Emanuel Avraam Matsaspt_BR
dc.contributor.referee3Sérgio Eduardo de Carvalho Eyer Joráspt_BR
dc.contributor.referee4Giancarlo Queiroz Pellegrinopt_BR
dc.creatorGustavo Henrique Costa de Souzapt_BR
dc.creator.Latteshttp://lattes.cnpq.br/1982291012091908pt_BR
dc.date.accessioned2023-04-04T12:14:43Z-
dc.date.available2023-04-04T12:14:43Z-
dc.date.issued2015-03-03-
dc.identifier.urihttp://hdl.handle.net/1843/51529-
dc.description.resumoWe investigate the relationship between orbital instability and decoherence in de Sitter (dS) spacetime. We consider a simple quadratic toy model proposed by Brandenberger, Laflamme and Mijic of two interacting scalar fields in a dS background. It admits a modewise separation, with each mode consisting of a pair of nonautonomous coupled harmonic oscillators. We show that the (classical) maximal Lyapunov exponent of every mode equals the asymptotic rate of (quantum) von Neumann entropy production of each oscillator, assuming an initial vacuum. This allows us to establish a logarithmic divergence of the entropy modulated by the spacetime inflation rate, and to calculate the late times superhorizon relationship between entropy generation of an oscillator and the system's exponential orbit separation rate. The connection between orbital instability and the decoherence of an oscillator's state is also examined from the point of view of the nonclassical depth, a quantity that is related to the existence of a phase-space representation for it interpretable as a classical stochastic distribution. We prove that its superhorizon behavior is determined by the balance between single-mode squeezing and entropy. In this regime, the entropy of a mode and the system's exponential orbit separation rate increase significantly as one moves from the weak- to the strong-coupling limit. If this increase is large enough for the entropy of an oscillator to grow more rapidly than squeezing, for example in the strong-coupling limit for not too high frequencies, the noise of every quadrature of the asymptotic state will be larger than the vacuum noise (zero nonclassical depth). The results suggest the possibility that simple, nonlinear interacting physical processes with unstable or chaotic classical counterparts may provide an important contribution to the effectiveness of the classicalization of cosmological scalar fields during a dS stage of spacetime expansion.pt_BR
dc.description.sponsorshipCAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superiorpt_BR
dc.languageengpt_BR
dc.publisherUniversidade Federal de Minas Geraispt_BR
dc.publisher.countryBrasilpt_BR
dc.publisher.departmentICX - DEPARTAMENTO DE FÍSICApt_BR
dc.publisher.programPrograma de Pós-Graduação em Físicapt_BR
dc.publisher.initialsUFMGpt_BR
dc.rightsAcesso Abertopt_BR
dc.subjectQuantum fields in curved spacetimespt_BR
dc.subjectDecoherencept_BR
dc.subjectClassicalization of quantum statespt_BR
dc.subject.otherDecoerênciapt_BR
dc.subject.otherSistemas quânticos abertospt_BR
dc.titleRelation between Lyapunov exponents and decoherence for real scalar fields in De Sitter spacetimept_BR
dc.typeTesept_BR
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