{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"16cd90393f7fa9105b42047c569bbbb847f87413f470a4e7eb35bc42bd62ca54","created":"2026-10-03T07:18:04Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"07aa9ae7b137f6569003f05e7e5552205e695382ec53b3ca6c4b0ba26045f9ff","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"fluid.quantum-turbulence.zero-temperature-dissipation","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Even at absolute zero, where superfluid helium has no viscosity, a vortex tangle decays as if the fluid had an effective viscosity. Its size, and why it differs between kinds of tangles, has not been calculated.","posed_since":"2008","precise":"For a homogeneous vortex tangle in 4He at $T\\to 0$ with line density $L$, define the effective kinematic viscosity nu' by the energy decay rate $\\epsilon=\\nu'(\\kappa L)^2$, with $\\kappa=h/m_4$. Calculate $\\nu'/\\kappa$ from the microscopic dissipation channels (reconnections, Kelvin-wave cascade, phonon emission) for quasiclassical (Kolmogorov) and ultraquantum (Vinen) tangles, and explain why the measured values differ between the two (Walmsley and Golov 2008).","problem_ref":null,"references":"","settled_by":"A calculation from vortex-filament or Gross-Pitaevskii dynamics reproducing measured $\\nu'/\\kappa$ for both tangle types within a factor of 2.","status_note":"","title":"Effective viscosity of superfluid turbulence at zero temperature","topic_ref":"cfe86b913c28db61b8da643149e508af2654c7237f0b6efa1efaa4c2c1fe95b1"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"22493647f997239482999b5bf407d81c70b4a1fd66f30c83f34a5f134637c032","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"8f820b88ae5b404c5f3a97ca67931cf9b9db7b20e7252e0949ec4497c200f488","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Pd0FDb4Bs8ICLuf6_uU4pUfNe54r3sZykf1ElE5sYiK0Ueck6RIyzMD3wuA464StphXaHjKoOenH3jP862wwBQ"},"schema":"pubphys.envelope/1"},"record_hash":"22493647f997239482999b5bf407d81c70b4a1fd66f30c83f34a5f134637c032","leaf_index":1423}