{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"b0f23de81e1e247cda1c5b0cff04d40a293afd2dfad7e4cd97a066f29f1b0911","created":"2026-10-03T07:17:54Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"dbad418ff46bf2c791c9f0f05fe264d1303a72b26dc2932bfdcc410e898f61bd","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"amo.unitary-fermi-transport.critical-second-sound","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"In a superfluid, heat travels as a wave (second sound). Near the transition its damping should grow following a universal law that has not been measured.","posed_since":"","precise":"At the unitary superfluid transition (3D XY static class), dynamic scaling predicts divergence of the thermal conductivity and second-sound diffusivity $D_{2}$ near $T_{c}$ with exponents set by the dynamic universality class (model F of Hohenberg-Halperin). Measure $D_{2}(T)$ for $\\left|T - T_{c}\\right|/T_{c}$ from 0.3 to 0.01 and extract the exponent. Answer: exponent with error and the class it identifies.","problem_ref":null,"references":"","settled_by":"Uniform-box second-sound spectroscopy with temperature resolution of order 1% of $T_c$ near the transition.","status_note":"Second-sound attenuation was measured through $T_{c}$ in uniform gases (Li et al., Science 2022), and thermography resolved a peak in second-sound diffusivity at $T_{c}$ (Yan et al., Science 2024); no critical exponent has been extracted.","title":"Critical behavior of second-sound damping at the superfluid transition","topic_ref":"b4f1be3df3747cf1d62d5ccbaa2ed5e283f70c00fc559fc9419649add747e05b"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"242e2810eaf2a33661b97fc425190c2616bf715d4e69a41a2429ca66a310805f","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"07063cad5ef1fd390142e85e86ec9db84f4916aff52caa59f2eba3a9af083c82","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"qi9m4dphjmkqi_81TQXAVhBLMB6FvoC-2SEPeNlm5QNH6zLNEJGlASfcQWDt7M8pfaQi-eyTUD-ke1K4qhmbAg"},"schema":"pubphys.envelope/1"},"record_hash":"242e2810eaf2a33661b97fc425190c2616bf715d4e69a41a2429ca66a310805f","leaf_index":473}