{
  "annotation_id": "715ef17c-9f53-40b6-b1f7-d6f582157d15",
  "date_created": "2026-03-02T18:00:53.406000Z",
  "date_modified": "2026-03-02T18:00:53.406000Z",
  "file_hash": "10c73564d542b55cd5d20f64823e197f5fb5a2bb6be89bd1fbedfd37b84ae6c5",
  "private": false,
  "record": {
    "abstract": "Reference arXiv:physics/0408021 claims that matter--free regions of spacetime\nmay support electromagnetic waves for which the phase velocity 3-vector is\noppositely directed to the power flow 3-vector. This was the definition of\nnegative refraction adopted in \\cite{ML}. We here show that this cannot occur\nin regions of spacetime for which the electromagnetic energy density is\npositive.",
    "arxiv_id": "physics/0410007",
    "authors": [
      "Martin W McCall"
    ],
    "categories": [
      "physics.optics",
      "physics.space-ph"
    ],
    "doi": "10.1088/0305-4470/38/11/N01",
    "journal_ref": "J.Phys. A38 (2005) 2543-2544",
    "title": "Comment on \u0027Towards gravitationally assisted negative refraction of   light by vacuum\u0027",
    "url": "https://arxiv.org/abs/physics/0410007"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "c9c21725-7602-4836-995f-cfc4674d8543",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}