{"state_type":"pith_open_graph_state","state_version":"1.0","pith_number":"pith:2015:277XE7SQQT5RZPEXMTRCPCRJJC","merge_version":"pith-open-graph-merge-v1","event_count":2,"valid_event_count":2,"invalid_event_count":0,"equivocation_count":0,"current":{"canonical_record":{"metadata":{"abstract_canon_sha256":"7ac6c65dbfc0abca0f1576519bd4facc181c0554545d0c6420265a7af6f28bca","cross_cats_sorted":[],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"math.OC","submitted_at":"2015-07-07T10:28:46Z","title_canon_sha256":"b5c9785cf8975801c6deb792e86108331bfc170fe7b7405215ca6ba35db31002"},"schema_version":"1.0","source":{"id":"1507.01741","kind":"arxiv","version":2}},"source_aliases":[{"alias_kind":"arxiv","alias_value":"1507.01741","created_at":"2026-05-18T01:19:00Z"},{"alias_kind":"arxiv_version","alias_value":"1507.01741v2","created_at":"2026-05-18T01:19:00Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.1507.01741","created_at":"2026-05-18T01:19:00Z"},{"alias_kind":"pith_short_12","alias_value":"277XE7SQQT5R","created_at":"2026-05-18T12:28:59Z"},{"alias_kind":"pith_short_16","alias_value":"277XE7SQQT5RZPEX","created_at":"2026-05-18T12:28:59Z"},{"alias_kind":"pith_short_8","alias_value":"277XE7SQ","created_at":"2026-05-18T12:28:59Z"}],"graph_snapshots":[{"event_id":"sha256:34a2a18aad022b291165d7c93be4340fdff00582ba9923c5c64f600f7406f8a3","target":"graph","created_at":"2026-05-18T01:19:00Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"graph_snapshot":{"author_claims":{"count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","strong_count":0},"builder_version":"pith-number-builder-2026-05-17-v1","claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"paper":{"abstract_excerpt":"The standard approach for photoacoustic imaging with variable speed of sound is time reversal, which consists in solving a well-posed final-boundary value problem for the wave equation backwards in time. This paper investigates the iterative Landweber regularization algorithm, where convergence is guaranteed by standard regularization theory, notably also in cases of trapping sound speed or for short measurement times. We formulate and solve the direct and inverse problem on the whole Euclidean space, what is common in standard photoacoustic imaging, but not for time-reversal algorithms, where","authors_text":"Otmar Scherzer, Thomas Glatz, Zakaria Belhachmi","cross_cats":[],"headline":"","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"math.OC","submitted_at":"2015-07-07T10:28:46Z","title":"A Direct Method for Photoacoustic Tomography with Inhomogeneous Sound Speed"},"references":{"count":0,"internal_anchors":0,"resolved_work":0,"sample":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1507.01741","kind":"arxiv","version":2},"verdict":{"created_at":null,"id":null,"model_set":{},"one_line_summary":"","pipeline_version":null,"pith_extraction_headline":"","strongest_claim":"","weakest_assumption":""}},"verdict_id":null}}],"author_attestations":[],"timestamp_anchors":[],"storage_attestations":[],"citation_signatures":[],"replication_records":[],"corrections":[],"mirror_hints":[],"record_created":{"event_id":"sha256:2117fbf042038a9cd2ce2d938d67b0f2d52566a6f922f86998ce8858dc79097f","target":"record","created_at":"2026-05-18T01:19:00Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"attestation_state":"computed","canonical_record":{"metadata":{"abstract_canon_sha256":"7ac6c65dbfc0abca0f1576519bd4facc181c0554545d0c6420265a7af6f28bca","cross_cats_sorted":[],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"math.OC","submitted_at":"2015-07-07T10:28:46Z","title_canon_sha256":"b5c9785cf8975801c6deb792e86108331bfc170fe7b7405215ca6ba35db31002"},"schema_version":"1.0","source":{"id":"1507.01741","kind":"arxiv","version":2}},"canonical_sha256":"d7ff727e5084fb1cbc9764e2278a294899f9ff1b24a99d73f9d596bba93383a5","receipt":{"algorithm":"ed25519","builder_version":"pith-number-builder-2026-05-17-v1","canonical_sha256":"d7ff727e5084fb1cbc9764e2278a294899f9ff1b24a99d73f9d596bba93383a5","first_computed_at":"2026-05-18T01:19:00.398796Z","key_id":"pith-v1-2026-05","kind":"pith_receipt","last_reissued_at":"2026-05-18T01:19:00.398796Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","receipt_version":"0.3","signature_b64":"E19EHbTEDbi5+n3HTZz4L+dc7Xn5SPseirwVIR+eTjdlFJUdxD4+5rcSJoZQEzJyaxkRIH3VZmDzpdvTdhtZDQ==","signature_status":"signed_v1","signed_at":"2026-05-18T01:19:00.399281Z","signed_message":"canonical_sha256_bytes"},"source_id":"1507.01741","source_kind":"arxiv","source_version":2}}},"equivocations":[],"invalid_events":[],"applied_event_ids":["sha256:2117fbf042038a9cd2ce2d938d67b0f2d52566a6f922f86998ce8858dc79097f","sha256:34a2a18aad022b291165d7c93be4340fdff00582ba9923c5c64f600f7406f8a3"],"state_sha256":"15424ca9b6e35ecfdafeaa1c0e8f8df803b32009fa62e60712e442cbe9b85369"}