{
  "annotation_id": "75481d19-942d-4c02-8c5d-1d6444158be9",
  "date_created": "2026-03-02T18:02:30.149000Z",
  "date_modified": "2026-03-02T18:02:30.149000Z",
  "file_hash": "7728b58627f7a51600a7a25c805d54133279bcd15428fb72a7f4dda04f90af80",
  "private": false,
  "record": {
    "abstract": "Entanglement in the ground state of the XY model on the infinite chain can be\nmeasured by the von Neumann entropy of a block of neighboring spins. We study a\ndouble scaling limit: the size of the block is much larger then 1 but much\nsmaller then the length of the whole chain. The entropy of the block has an\nasymptotic limit. We study this limiting entropy as a function of the\nanisotropy and of the magnetic field. We identify its minima at product states\nand its divergencies at the quantum phase transitions. We find that the curves\nof constant entropy are ellipses and hyperbolas and that they all meet at one\npoint (essential critical point). Depending on the approach to the essential\ncritical point the entropy can take any value between 0 and infinity. In the\nvicinity of this point small changes in the parameters cause large change of\nthe entropy.",
    "arxiv_id": "quant-ph/0609098",
    "authors": [
      "F. Franchini",
      "A. R. Its",
      "B. -Q. Jin",
      "V. E. Korepin"
    ],
    "categories": [
      "quant-ph",
      "cond-mat.stat-mech",
      "hep-th",
      "math-ph",
      "math.MP"
    ],
    "doi": "10.1088/1751-8113/40/29/019",
    "journal_ref": "J. Phys. A: Math. Theor. 40 (2007) 8467-8478",
    "title": "Ellipses of Constant Entropy in the XY Spin Chain",
    "url": "https://arxiv.org/abs/quant-ph/0609098"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "1ac56a00-1266-4e54-911f-737b1832f236",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}