{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"ca9ec33955c23f625b7c9b5a43a18c5813171e89ff42605f7fe1b818deb0ffbb","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["4fc1111f295375647f80e05235178e90b3a607128874c44e674a982642eedfbd","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"7837228c76853e5ce54b570a4aba455dbe55666733e4cc535fae636a8d9faf95","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":"2","parents":[],"plain":"Fluid models describe heavy-ion collisions starting about $3 \\times 10^{-24}$ 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":"4fc1111f295375647f80e05235178e90b3a607128874c44e674a982642eedfbd","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"639ee0a66e799dbc59423f515971ee234f484bff1e1c6aeae063e82e892cbb91","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"66e3d378f1ca428f574c64bb14f534a97fc6aae94f25a3440fab7031942cafc0","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"81A3hCIR70UHTTuYe3530dXEI5ga_HqdPCHkbDD_Xdp7-aKwi6d1HLiumMjOeGRcLYKi-pRM6lh0PqUsH2r_DA"},"schema":"pubphys.envelope/1"},"record_hash":"639ee0a66e799dbc59423f515971ee234f484bff1e1c6aeae063e82e892cbb91","leaf_index":3530}