{
  "annotation_id": "a398644f-2885-4f85-9906-040b907144ff",
  "date_created": "2026-03-02T18:00:57.242000Z",
  "date_modified": "2026-03-02T18:00:57.242000Z",
  "file_hash": "4b54b08be9c9740a825e94d411d6e775dfff4f328e5826886d603ee42fd1d40c",
  "private": false,
  "record": {
    "abstract": "We report a simple experiment of two-dimensional pattern formation in a\ncircular Hele-Shaw cell, showing the appearance of a return branch that is\nequivalent to the upward-connecting leader of lightning. Injecting water from\nthe center into a foam filled cell, we obtained patterns similar to dendrites\nof two-dimensional dielectric breakdown experiments. When we repeat this\nexperiment allowing the presence of water in the outer (low pressure) region,\ndendrites grow initially as in a normal experiment, but when a branch is near\nthe outer boundary, the low pressure water begins to penetrate the foam against\nthe pressure field, forming several return branches.",
    "arxiv_id": "physics/0505125",
    "authors": [
      "Francisco Vera"
    ],
    "categories": [
      "physics.flu-dyn",
      "nlin.PS"
    ],
    "title": "The return branch of viscous fingers",
    "url": "https://arxiv.org/abs/physics/0505125"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "6f46a75b-5f91-4a03-be3e-b421e803b3d1",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}