{
  "id": "cond-mat/0201505",
  "version": "v1",
  "published": "2002-01-28T15:09:20.000Z",
  "updated": "2002-01-28T15:09:20.000Z",
  "title": "A new expansion around mean field for the quantum Ising model",
  "authors": [
    "F. De Pasquale",
    "S. M. Giampaolo"
  ],
  "comment": "10 Pages + 2 Figs. Submitted to Prl",
  "categories": [
    "cond-mat.stat-mech"
  ],
  "abstract": "We show that an high temperature expansion at fixed order parameter can be derived for the quantum Ising model. The basic point is to consider a statistical generating functional associated to the local spin state. The probability at thermal equilibrium of this state reflects directly the occurrence of a spontaneous symmetry breaking. It is possible to recover the expansion around the mean field in the system dimensionality if the ``direction'' in the Hilbert space of local spin states is suitably chosen. Results for the free energy at the critical temperature, as a function of the transverse field, in first order approximation in the inverse system dimensionality are compared with those of the standard approach.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2002-01-28T15:09:20.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "quantum ising model",
      "mean field",
      "local spin state",
      "high temperature expansion",
      "first order approximation"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2002cond.mat..1505D"
    }
  }
}