889 research outputs found
Statistical Entropy Of Open Quantum Systems
Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Dissipative quantum systems are frequently described within the framework of the so-called "system-plusreservoir" approach. In this work we assign their description to the Maximum Entropy Formalism and compare the resulting thermodynamic properties with those of the well-established approaches. Due to the non-negligible coupling to the heat reservoir, these systems are nonextensive by nature, and the former task may require the use of nonextensive parameter dependent informational entropies. In doing so, we address the problem of choosing appropriate forms of those entropies in order to describe a consistent thermodynamics for dissipative quantum systems. Nevertheless, even having chosen the most successful and popular forms of those entropies, we have proven our model to be a counterexample where this sort of approach leads us to wrong results.946Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Fundacao de Amparo a Pesquisa no Estado de Sao Paulo (FAPESP) through the initiative Instituto Nacional de Ciencia e Tecnologia em Informacao Quantica (INCT-IQ)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES
Universal and anomalous behavior in the thermalization of strongly interacting harmonically trapped gas mixtures
We report on the dynamics of thermalization by extending a generalization of
the Caldeira-Leggett model, developed in the context of cold atomic gases
confined in a harmonic trap, to higher dimensions. Universal characteristics en
route to thermalization which appear to be independent of dimensionality are
highlighted, which additionally suggest a scaling analogous to turbulent mixing
in fluid dynamics. We then focus on features dependent on dimensionality, with
particular regard to the role of angular momentum of the two atomic clouds,
having in mind the goal of efficient thermalization between the two species.
Finally, by considering asymmetry in species numbers, we find that nonlinear
inter-species interactions provide a mode locking mechanism between the
majority and minority species, relevant to recent experiments involving
Fermi-Bose mixtures in the normal phase.Comment: 11 pages, 8 figures. Submitted to J.Phys.
Nonequilibrium thermodynamics in the strong coupling and non-Markovian regime based on a reaction coordinate mapping
We propose a method to study the thermodynamic behaviour of small systems
beyond the weak coupling and Markovian approximation, which is different in
spirit from conventional approaches. The idea is to redefine the system and
environment such that the effective, redefined system is again coupled weakly
to Markovian residual baths and thus, allows to derive a consistent
thermodynamic framework for this new system-environment partition. To achieve
this goal we make use of the reaction coordinate mapping, which is a general
method in the sense that it can be applied to an arbitrary (quantum or
classical and even time-dependent) system coupled linearly to an arbitrary
number of harmonic oscillator reservoirs. The core of the method relies on an
appropriate identification of a part of the environment (the reaction
coordinate), which is subsequently included as a part of the system. We
demonstrate the power of this concept by showing that non-Markovian effects can
significantly enhance the steady state efficiency of a three-level-maser heat
engine, even in the regime of weak system-bath coupling. Furthermore, we show
for a single electron transistor coupled to vibrations that our method allows
one to justify master equations derived in a polaron transformed reference
frame.Comment: updated and improved version; 19 pages incl. 10 figures and 5 pages
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