{"paper":{"title":"Universally and existentially definable subsets of global fields","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["math.LO"],"primary_cat":"math.NT","authors_text":"Kirsten Eisentraeger, Travis Morrison","submitted_at":"2016-09-30T16:05:12Z","abstract_excerpt":"We show that rings of $S$-integers of a global function field $K$ of odd characteristic are first-order universally definable in $K$. This extends work of Koenigsmann and Park who showed the same for $\\mathbb{Z}$ in $\\mathbb{Q}$ and the ring of integers in a number field, respectively.\n  We also give another proof of a theorem of Poonen and show that the set of non-squares in a global field of characteristic $\\neq 2$ is diophantine. Finally, we show that the set of pairs $(x,y)$ in $(K^{\\times})^2$ such that $x$ is not a norm in $K(\\sqrt{y})$ is diophantine over $K$ for any global field $K$ of"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1609.09787","kind":"arxiv","version":3},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"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"}