107 research outputs found

    On Generalized Bose-Einstein Condensation in the Almost-Ideal Boson Gas

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    We scrutinize an interparticle interaction which can create the type-I generalized Bose-Einstein condensation in spite of other thermodynamic properties of the model coinciding with those for the free boson gas

    The Canonical Perfect Bose Gas in Casimir Boxes

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    We study the problem of Bose-Einstein condensation in the perfect Bose gas in the canonical ensemble, in anisotropically dilated rectangular parallelpipeds (Casimir boxes). We prove that in the canonical ensemble for these anisotropic boxes there is the same type of generalized Bose-Einstein condensation as in the grand-canonical ensemble for the equivalent geometry. However the amount of condensate in the individual states is different in some cases and so are the fluctuations.Comment: 23 page

    A Pair Hamiltonian Model of a Non-ideal Boson Gas

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    The pressure in the thermodynamic limit of a non-ideal Boson gas whose Hamiltonian includes only diagonal and pairing terms can be expressed as the infimum of a functional depending on two measures on momentum space: a positive measure describing the particle density and a complex measure describing the pair density. In this paper we examine this variational problem with the object of determining when the model exhibits Bose-Einstein condensation. In addition we show that if the pairing term in the Hamiltonian is positive then it has no effect

    Dynamical Semigroups for Unbounded Repeated Perturbation of Open System

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    We consider dynamical semigroups with unbounded Kossakowski-Lindblad-Davies generators which are related to evolution of an open system with a tuned repeated harmonic perturbation. Our main result is the proof of existence of uniquely determined minimal trace-preserving strongly continuous dynamical semigroups on the space of density matrices. The corresponding dual W *-dynamical system is shown to be unital quasi-free and completely positive automorphisms of the CCR-algebra. We also comment on the action of dynamical semigroups on quasi-free states