{"paper":{"title":"An Improved Upper Bound on the Zarankiewicz Number z(43;2)","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["cs.DM"],"primary_cat":"math.CO","authors_text":"Ankan Sadhu","submitted_at":"2026-08-03T02:29:12Z","abstract_excerpt":"The Zarankiewicz number z(43;2) is the largest number of edges in a four-cycle-free bipartite graph with two parts of size 43. Reiman's bound gives z(43;2) <= 301, with equality only for the incidence graph of a projective plane of order six; no such plane exists, so z(43;2) <= 300. We prove z(43;2) <= 299. The argument is elementary and uses no computer search: a counting identity for the leave of the configuration shows that a hypothetical 300-edge graph admits one of exactly twenty-seven degree profiles per side, of which only four combinations are locally compatible. Three force two vertic"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2608.01606","kind":"arxiv","version":1},"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/2608.01606/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"}