Speaker
Description
The early thermalization puzzle—stemming from the unexpectedly early success of hydrodynamics in describing the quark–gluon plasma (QGP)—remains a central open question in relativistic heavy-ion collisions. To address this, we develop a new theoretical framework, the spectral BBGKY hierarchy, which is analytically equivalent to the Liouville equation and preserves time-reversal invariance while offering significant advantages for numerical implementation. This reformulation provides a semi-analytic route to non-equilibrium, nonlinear many-body dynamics, encompassing both the conventional Boltzmann description and explicit two-body correlations [1].
Applying this spectral nonlinear Boltzmann equation to a homogeneous massless system, we systematically investigated the timescales of linearization and thermalization. We identified a robust separation: the linearization time, at which the system begins to follow hydrodynamical evolution, is approximately half the thermalization time. This result provides a quantitative resolution to the early thermalization puzzle by demonstrating that hydrodynamic applicability commences once the system enters the linearized regime, well before full local thermal equilibrium is established. [2]
[1] arXiv: 2507.14243, Xingjian Lu, Shuzhe Shi.
[2] arXiv: 2509.xxxxx, Xingjian Lu, Shuzhe Shi.
