{"record_type":"pith_number_record","schema_url":"https://pith.science/schemas/pith-number/v1.json","pith_number":"pith:2007:H6H2LJETFVEXXTSZHOL6Y4OI2M","short_pith_number":"pith:H6H2LJET","schema_version":"1.0","canonical_sha256":"3f8fa5a4932d497bce593b97ec71c8d33edb7b57f013f825f59ed05405d4e55c","source":{"kind":"arxiv","id":"0710.5923","version":2},"attestation_state":"computed","paper":{"title":"Primary caustics and critical points behind a Kerr black hole","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["gr-qc"],"primary_cat":"astro-ph","authors_text":"F. De Luca (Univ. Zurich), M. Sereno","submitted_at":"2007-10-31T18:43:38Z","abstract_excerpt":"The primary optical caustic surface behind a Kerr black hole is a four-cusped tube displaced from the line of sight. We derive the caustic surface in the nearly asymptotic region far from the black hole through a Taylor expansion of the lightlike geodesics up to and including fourth-order terms in m/b and a/b, where $m$ is the black hole mass, a the spin and b the impact parameter. The corresponding critical locus in the observer's sky is elliptical and a point-like source inside the caustics will be imaged as an Einstein cross. With regard to lensing near critical points, a Kerr lens is analo"},"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":"0710.5923","kind":"arxiv","version":2},"metadata":{"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"astro-ph","submitted_at":"2007-10-31T18:43:38Z","cross_cats_sorted":["gr-qc"],"title_canon_sha256":"5093c26c53d8720ee2e46912fdfc100be0f7dca1856c3476cd748f0c9f206a93","abstract_canon_sha256":"994f7a2f9a74902c2906809ed665349a4eefe8987716cac628b4b93e70e2c836"},"schema_version":"1.0"},"receipt":{"kind":"pith_receipt","key_id":"pith-v1-2026-05","algorithm":"ed25519","signed_at":"2026-07-04T15:33:58.691423Z","signature_b64":"zB3hFPG88mWEZJ3EurYHQcSc8VHaT2Ry7TamHcAsL0B8fH9Y/5iirUSjFjvl+deCueRXnUjwxMbP6lSPlzx/Bg==","signed_message":"canonical_sha256_bytes","builder_version":"pith-number-builder-2026-05-17-v1","receipt_version":"0.3","canonical_sha256":"3f8fa5a4932d497bce593b97ec71c8d33edb7b57f013f825f59ed05405d4e55c","last_reissued_at":"2026-07-04T15:33:58.690960Z","signature_status":"signed_v1","first_computed_at":"2026-07-04T15:33:58.690960Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"graph_snapshot":{"paper":{"title":"Primary caustics and critical points behind a Kerr black hole","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["gr-qc"],"primary_cat":"astro-ph","authors_text":"F. De Luca (Univ. Zurich), M. Sereno","submitted_at":"2007-10-31T18:43:38Z","abstract_excerpt":"The primary optical caustic surface behind a Kerr black hole is a four-cusped tube displaced from the line of sight. We derive the caustic surface in the nearly asymptotic region far from the black hole through a Taylor expansion of the lightlike geodesics up to and including fourth-order terms in m/b and a/b, where $m$ is the black hole mass, a the spin and b the impact parameter. The corresponding critical locus in the observer's sky is elliptical and a point-like source inside the caustics will be imaged as an Einstein cross. With regard to lensing near critical points, a Kerr lens is analo"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"0710.5923","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/0710.5923/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":"0710.5923","created_at":"2026-07-04T15:33:58.691027+00:00"},{"alias_kind":"arxiv_version","alias_value":"0710.5923v2","created_at":"2026-07-04T15:33:58.691027+00:00"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.0710.5923","created_at":"2026-07-04T15:33:58.691027+00:00"},{"alias_kind":"pith_short_12","alias_value":"H6H2LJETFVEX","created_at":"2026-07-04T15:33:58.691027+00:00"},{"alias_kind":"pith_short_16","alias_value":"H6H2LJETFVEXXTSZ","created_at":"2026-07-04T15:33:58.691027+00:00"},{"alias_kind":"pith_short_8","alias_value":"H6H2LJET","created_at":"2026-07-04T15:33:58.691027+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/H6H2LJETFVEXXTSZHOL6Y4OI2M","json":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M.json","graph_json":"https://pith.science/api/pith-number/H6H2LJETFVEXXTSZHOL6Y4OI2M/graph.json","events_json":"https://pith.science/api/pith-number/H6H2LJETFVEXXTSZHOL6Y4OI2M/events.json","paper":"https://pith.science/paper/H6H2LJET"},"agent_actions":{"view_html":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M","download_json":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M.json","view_paper":"https://pith.science/paper/H6H2LJET","resolve_alias":"https://pith.science/api/pith-number/resolve?arxiv=0710.5923&json=true","fetch_graph":"https://pith.science/api/pith-number/H6H2LJETFVEXXTSZHOL6Y4OI2M/graph.json","fetch_events":"https://pith.science/api/pith-number/H6H2LJETFVEXXTSZHOL6Y4OI2M/events.json","actions":{"anchor_timestamp":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M/action/timestamp_anchor","attest_storage":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M/action/storage_attestation","attest_author":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M/action/author_attestation","sign_citation":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M/action/citation_signature","submit_replication":"https://pith.science/pith/H6H2LJETFVEXXTSZHOL6Y4OI2M/action/replication_record"}},"created_at":"2026-07-04T15:33:58.691027+00:00","updated_at":"2026-07-04T15:33:58.691027+00:00"}