{"record_type":"pith_number_record","schema_url":"https://pith.science/schemas/pith-number/v1.json","pith_number":"pith:2003:VVFGDQ2UE46XUOCHD4JIIH367I","short_pith_number":"pith:VVFGDQ2U","schema_version":"1.0","canonical_sha256":"ad4a61c354273d7a38471f12841f7efa2aa3bbbb6b5e6d8a780fd9ce3a189cc5","source":{"kind":"arxiv","id":"gr-qc/0307063","version":2},"attestation_state":"computed","paper":{"title":"Maxwell's field coupled nonminimally to quadratic torsion: Induced axion field and birefringence of the vacuum","license":"","headline":"","cross_cats":[],"primary_cat":"gr-qc","authors_text":"Friedrich W. Hehl, Yakov Itin","submitted_at":"2003-07-13T08:48:43Z","abstract_excerpt":"We consider a possible (parity conserving) interaction between the electromagnetic field $F$ and a torsion field $T^\\alpha$ of spacetime. For generic elementary torsion, gauge invariant coupling terms of lowest order fall into two classes that are both nonminimal and {\\it quadratic} in torsion. These two classes are displayed explicitly. The first class of the type $\\sim F T^2$ yields (undesirable) modifications of the Maxwell equations. The second class of the type $\\sim F^2 T^2$ doesn't touch the Maxwell equations but rather modifies the constitutive tensor of spacetime. Such a modification "},"verification_status":{"content_addressed":true,"pith_receipt":true,"author_attested":false,"weak_author_claims":0,"strong_author_claims":0,"externally_anchored":false,"storage_verified":false,"citation_signatures":0,"replication_records":0,"graph_snapshot":true,"references_resolved":false,"formal_links_present":false},"canonical_record":{"source":{"id":"gr-qc/0307063","kind":"arxiv","version":2},"metadata":{"license":"","primary_cat":"gr-qc","submitted_at":"2003-07-13T08:48:43Z","cross_cats_sorted":[],"title_canon_sha256":"244b6caf7567bd11e241cf0f8b2cd08e8355a18195c7ff17d13e4ab3271c58ce","abstract_canon_sha256":"abe812bef8d4986804700424e7251eb0e7f16725420a2d7fe555f7d05ed6d544"},"schema_version":"1.0"},"receipt":{"kind":"pith_receipt","key_id":"pith-v1-2026-05","algorithm":"ed25519","signed_at":"2026-07-04T16:40:15.019233Z","signature_b64":"fO2+TCujftvD7b+kNyOVla+WdMhlhrS+3k7Kr8Pc96GpEp3gtNfilwnHg55Xn1oYRzFSrdgCmGehXKOkSzrnBw==","signed_message":"canonical_sha256_bytes","builder_version":"pith-number-builder-2026-05-17-v1","receipt_version":"0.3","canonical_sha256":"ad4a61c354273d7a38471f12841f7efa2aa3bbbb6b5e6d8a780fd9ce3a189cc5","last_reissued_at":"2026-07-04T16:40:15.018864Z","signature_status":"signed_v1","first_computed_at":"2026-07-04T16:40:15.018864Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"graph_snapshot":{"paper":{"title":"Maxwell's field coupled nonminimally to quadratic torsion: Induced axion field and birefringence of the vacuum","license":"","headline":"","cross_cats":[],"primary_cat":"gr-qc","authors_text":"Friedrich W. Hehl, Yakov Itin","submitted_at":"2003-07-13T08:48:43Z","abstract_excerpt":"We consider a possible (parity conserving) interaction between the electromagnetic field $F$ and a torsion field $T^\\alpha$ of spacetime. For generic elementary torsion, gauge invariant coupling terms of lowest order fall into two classes that are both nonminimal and {\\it quadratic} in torsion. These two classes are displayed explicitly. The first class of the type $\\sim F T^2$ yields (undesirable) modifications of the Maxwell equations. The second class of the type $\\sim F^2 T^2$ doesn't touch the Maxwell equations but rather modifies the constitutive tensor of spacetime. Such a modification "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"gr-qc/0307063","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/gr-qc/0307063/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"},"aliases":[{"alias_kind":"arxiv","alias_value":"gr-qc/0307063","created_at":"2026-07-04T16:40:15.018926+00:00"},{"alias_kind":"arxiv_version","alias_value":"gr-qc/0307063v2","created_at":"2026-07-04T16:40:15.018926+00:00"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.gr-qc/0307063","created_at":"2026-07-04T16:40:15.018926+00:00"},{"alias_kind":"pith_short_12","alias_value":"VVFGDQ2UE46X","created_at":"2026-07-04T16:40:15.018926+00:00"},{"alias_kind":"pith_short_16","alias_value":"VVFGDQ2UE46XUOCH","created_at":"2026-07-04T16:40:15.018926+00:00"},{"alias_kind":"pith_short_8","alias_value":"VVFGDQ2U","created_at":"2026-07-04T16:40:15.018926+00:00"}],"events":[],"event_summary":{},"paper_claims":[],"inbound_citations":{"count":0,"internal_anchor_count":0,"sample":[]},"formal_canon":{"evidence_count":0,"sample":[],"anchors":[]},"links":{"html":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I","json":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I.json","graph_json":"https://pith.science/api/pith-number/VVFGDQ2UE46XUOCHD4JIIH367I/graph.json","events_json":"https://pith.science/api/pith-number/VVFGDQ2UE46XUOCHD4JIIH367I/events.json","paper":"https://pith.science/paper/VVFGDQ2U"},"agent_actions":{"view_html":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I","download_json":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I.json","view_paper":"https://pith.science/paper/VVFGDQ2U","resolve_alias":"https://pith.science/api/pith-number/resolve?arxiv=gr-qc/0307063&json=true","fetch_graph":"https://pith.science/api/pith-number/VVFGDQ2UE46XUOCHD4JIIH367I/graph.json","fetch_events":"https://pith.science/api/pith-number/VVFGDQ2UE46XUOCHD4JIIH367I/events.json","actions":{"anchor_timestamp":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I/action/timestamp_anchor","attest_storage":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I/action/storage_attestation","attest_author":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I/action/author_attestation","sign_citation":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I/action/citation_signature","submit_replication":"https://pith.science/pith/VVFGDQ2UE46XUOCHD4JIIH367I/action/replication_record"}},"created_at":"2026-07-04T16:40:15.018926+00:00","updated_at":"2026-07-04T16:40:15.018926+00:00"}