{
  "id": "1510.01985",
  "version": "v1",
  "published": "2015-10-07T15:27:15.000Z",
  "updated": "2015-10-07T15:27:15.000Z",
  "title": "Diagrammatic description of a quantum system coupled to strong noise",
  "authors": [
    "Michael Marthaler",
    "Juha Leppäkangas"
  ],
  "comment": "8 pages",
  "categories": [
    "cond-mat.mes-hall",
    "quant-ph"
  ],
  "abstract": "We study a system-bath description in the strong coupling regime, where it is not possible to derive a master equation for the reduced density matrix by a direct expansion in the system-bath coupling. A particular example is a bath with significant spectral weight at low frequencies. Through an unitary transformation it can be possible to find a more suitable small expansion parameter. Within this approach we construct a formally exact expansion of the master equation on the Keldysh contour. The lowest-order expansion is similar to the so-called $P(E)$-theory or non-interacting blip approximation (NIBA). The analysis of the higher-order contributions shows that there are two different classes of higher-order diagrams. We study how the form of the spectral function affects their convergence.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-10-07T15:27:15.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "quantum system",
      "strong noise",
      "diagrammatic description",
      "master equation",
      "significant spectral weight"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015arXiv151001985M"
    }
  }
}