{
  "annotation_id": "0ad88b5c-7dce-4487-a314-4b91ce348efc",
  "date_created": "2026-03-02T18:00:53.461000Z",
  "date_modified": "2026-03-02T18:00:53.461000Z",
  "file_hash": "d9b55714b5f0137d7be5ae69a06873d3bbc3efac7967670b104e005344226be0",
  "private": false,
  "record": {
    "abstract": "The Maxwell equations are formulated in a generally covariant and metric-free\nway in 1+3 and subsequently in 4 dimensions. For this purpose, we use the\nexcitations $\\cal D$, $\\cal H$ and the field strengths $E,B$. A local and\nlinear constitutive law between excitations and field strengths is assumed,\nwith a constitutive tensor $\\chi^{ijkl}=-\\chi^{jikl}=-\\chi^{ijlk}$ of 36\ncomponents. The properties of this tensor are discussed. In particular, we\naddress the validity of the Post constraint, a subject that is very much under\ndiscussion. In this connection, the Tellegen gyrator, the axion field, and the\n``perfect electromagnetic conductor\u0027\u0027 of Lindell \u0026 Sihvola are compared with\neach other.",
    "arxiv_id": "physics/0411038",
    "authors": [
      "Friedrich W. Hehl",
      "Yuri N. Obukhov"
    ],
    "categories": [
      "physics.class-ph",
      "cond-mat.mtrl-sci",
      "gr-qc",
      "physics.gen-ph"
    ],
    "doi": "10.1016/j.physleta.2004.11.038",
    "journal_ref": "Phys.Lett. A334 (2005) 249-259",
    "title": "Linear media in classical electrodynamics and the Post constraint",
    "url": "https://arxiv.org/abs/physics/0411038"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "5a71bad6-3bd7-404e-918d-da06e186e651",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}