{
  "annotation_id": "929e19a5-0d70-4ae8-98ea-1a115ae81d02",
  "date_created": "2026-03-02T18:00:25.252000Z",
  "date_modified": "2026-03-02T18:00:25.252000Z",
  "file_hash": "61002bf7ea6a6cbc66123d622ac5fa93d0e10d6676c6a2fd216f5a60420d7f3b",
  "private": false,
  "record": {
    "abstract": "We apply boson expansion methods to an extended Lipkin-Meshkov-Glick model\nincluding anharmonicities in analogy with previous microscopic calculations. We\nstudy the effects of different approximations present in these calculations,\namong which the truncation of the hamiltonian and of the space, in connection\nwith the study of the properties of two-phonon and three-phonon states. By\ncomparing the approximate results on the spectrum with the exact ones we\nconclude that the approximations made in the microscopic calculations on\ntwo-phonon states are well justified. We find also that a good agreement with\nthe exact results for the three-phonon state is obtained by using a bosonic\nhamiltonian truncated at the fourth order. This result makes us confident that\nsuch approximation can be used in realistic calculations, thus allowing a\ntheoretical study of triple excitations of giant resonances.",
    "arxiv_id": "nucl-th/9811083",
    "authors": [
      "C. Volpe",
      "Ph. Chomaz",
      "M. V. Andres",
      "F. Catara",
      "E. G. Lanza"
    ],
    "categories": [
      "nucl-th"
    ],
    "doi": "10.1016/S0375-9474(99)00016-0",
    "journal_ref": "Nucl.Phys. A647 (1999) 246-256",
    "title": "Boson expansion methods applied to a two-level model in the study of   multiple giant resonances",
    "url": "https://arxiv.org/abs/nucl-th/9811083"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "197c60e5-e7fb-4081-9204-042096f348ec",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}