{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"be793710a9098539703646c37f94778ec10f688c74fb6240d7c1aa7bcc160cf6","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"5ac9e3fc2191b3a78aa6144ed4404e52d558911a1337adf64ee115c7f8a15ba6","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"nuc.quark-gluon-plasma.early-hydrodynamization","kind":"phenomenon","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Fluid models describe heavy-ion collisions starting about 3e-24 seconds after impact, which seems too early for the matter to have settled down. How the system starts behaving as a fluid so soon is not fully understood.","posed_since":"","precise":"Determine how and when the energy-momentum tensor of matter formed in $A+A$ collisions reaches viscous-hydrodynamic form (hydrodynamization) while the pressure anisotropy $P_L/P_T$ is still far from 1, at proper times $\\tau$ about $0.5\\ \\text{to}\\ 1\\ \\mathrm{fm}/c$. Answer: a QCD-based mechanism (attractor solutions, weak-coupling kinetic theory, or strong-coupling holography) with a predicted hydrodynamization time as a function of $\\eta/s$ and energy density, tested against data.","problem_ref":null,"references":"","settled_by":"QCD effective kinetic theory simulations with realistic transverse geometry, compared with photon and dilepton data sensitive to the early pressure anisotropy.","status_note":"Hydrodynamic attractor solutions found since 2015 (Heller and Spalinski) explain early hydrodynamic behavior in simplified expansions; the full three-dimensional QCD case remained open as of 2026.","title":"How the quark-gluon plasma becomes a fluid so quickly","topic_ref":"ec5bb29d3c4ec6576273c8009fdd00011a21f5672430b3080013ab67a0a1a41c"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"4fc1111f295375647f80e05235178e90b3a607128874c44e674a982642eedfbd","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"2c7d319092a81da44c0e398770a9b4ab6943a370aee498b730c0add47e7efebc","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"j01clvdXO_YnJUAOQPwEHc4ZVZfFweCyHhxPfDU9frBWoDl-N7vEkYr5z2XgYyor9sFkKWWr7VC7qOrYnaIjCA"},"schema":"pubphys.envelope/1"},"record_hash":"4fc1111f295375647f80e05235178e90b3a607128874c44e674a982642eedfbd","leaf_index":1803}