{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"fd3905da0c027cd7cad5597a64a1112ff741b7e06626cdc9ac4ef1d1d232cff5","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["494b3b4a46867e7fcd130a4ba1e211152783c5f51fd08f0d9c721e9a6da663f3","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"85783be89937223e23eb7110d033bbe5dcf5b84efd7b50985539a25c5a151a86","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"cm.sign-problem-numerics.intrinsic-sign-problem","kind":"well-posed","literature_status":"partially-resolved","n":"2","parents":[],"plain":"Many phases of matter with one-way edge currents provably cannot be simulated sign-free by any model built from local terms. Which other phases share this obstruction is open.","posed_since":"2017","precise":"Ringel and Kovrizhin (2017) and Golan, Smith and Ringel (2020) showed that chiral topological phases for which exp(2 pi i c/24) (c the chiral central charge) differs from every topological spin cannot be realized by any local sign-free Hamiltonian. Determine whether non-chiral topological orders, gapless phases (e.g. non-Fermi liquids or Fermi surfaces with nontrivial Luttinger volume) or symmetry-enriched phases carry intrinsic sign problems, and give a complete criterion. An answer is a classification with proofs.","problem_ref":"494b3b4a46867e7fcd130a4ba1e211152783c5f51fd08f0d9c721e9a6da663f3","references":"","settled_by":"A theorem extending the chiral criterion to all gapped phases, or explicit sign-free local models for the remaining phases.","status_note":"The chiral case covered by the topological-spin criterion was settled by 2020; non-chiral and gapless cases remain open.","title":"Which phases of matter carry an intrinsic sign problem?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"b32132958774e9823c1fa99cbd7600759f0e551584c587a8fc73d0c38f433584","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a25023d04e8e6cbf566486fb5ed339731e8d78319253251d177ce2c409db97a4","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"VQeV_JcEM7U720xnbhA9l23PkD1Obym8x63hQR-czK0t8F4cP8wuk3Lq6iz-15NCkcS_UkFWebfBxdtLO1yrAA"},"schema":"pubphys.envelope/1"},"record_hash":"b32132958774e9823c1fa99cbd7600759f0e551584c587a8fc73d0c38f433584","leaf_index":3028}