• Oct 20 2010

    Seminar at UCT on Wednesday 20 October 12:00 to 13:00

    Title: Nonequivalence of ensembles for long-range quantum spin systems in optical lattices

    on Wednesday, Michael Kastner, NITheP, will give a presentation on

    Nonequivalence of ensembles for long-range quantum spin systems in optical lattices

    Motivated by the anisotropic long-range nature of the interactions between cold dipolar atoms or molecules in an optical lattice, the anisotropic quantum Heisenberg model with Curie-Weiss-type long-range interactions is studied. Conservation of energy in optical lattice experiments suggests a study of this model within the microcanonical ensemble. The microcanonical entropy is calculated analytically and, depending on the choice of the anisotropy parameters, microcanonical and canonical ensembles are equivalent in some cases, and not equivalent in others. From the shape of the entropy it follows that the Curie-Weiss Heisenberg model is indistinguishable from the Curie-Weiss Ising model in canonical thermodynamics, although their microcanonical thermodynamics in general differs. Qualitatively, the observed features of nonequivalent ensembles are expected to be relevant for a large class of long-range quantum spin systems, and in particular for the correct interpretation of the results from optical lattice experiments modeling such systems.


    when: Wed, 20 October 2010, 12:00 to 13:00

    where: UCT, Duncan Elliott Seminar Room, RW James Building

    All welcome!