题目：Thermalization of the Wigner function--- a real time, non-perturbative quantum simulation based on the Schwinger Model

报告人：Shile Chen（清华大学博士后研究员）

报告时间：2024年7月22日 周一 10:30

报告地点：格致楼3005

联系人：李峰

报告摘要：研究产生于相对论性重离子对撞(HIC)中的夸克-胶子等离子体的热化过程是一个关键的理论问题，它对于理解HIC中流体过程的初始状态，以及更广泛地说，探索量子系统的热化都至关重要。 人们需要一种实时、非微扰的方法，从而在理论上以第一性原理的视角解决此问题。为此，我们在经典硬件上对一个有质量的 Schwinger 模型进行了完全的量子模拟。该模型具有禁闭与自发手征对称性破缺等重要特性，因此能很好地模仿量子色动力学 （QCD）。我们的研究专注于 Wigner 函数的实时演化。Wigner函数即夸克场的两点相关函数，它可被近似理解为夸克的相空间分布函数。开始于一个非平衡初始状态，Wigner 函数以及纠缠熵的实时演化都表明，量子系统的热化是可行的。特别是，在量子涨落存在的情况下，达到热化状态的弛豫依赖于耦合强度。我们还研究了 Wigner 函数热化与众所周知的本征态热化之间的联系。

 Thermalization of the quark gluon plasma created in relativistic heavy-ion collisions is a crucial theoretical question in understanding the onset of hydrodynamics, and in a broad sense, a key step to the exploration of thermalization in quantum systems. Addressing this problem theoretically, in a first principle manner, requires a real-time, non-perturbative method. To this end, we carry out a fully quantum simulation on a classical hardware, of a massive Schwinger model, which well mimics QCD as it shares the important properties such as confinement and chiral symmetry breaking. We focus on the real-time evolution of the Wigner function, namely, the two-point correlation function, which approximates quark momentum distribution, etc. Starting from a non-equilibrium initial state, the real time evolution of the Wigner functions, as well as the entanglement entropy, both demonstrate that thermalization of the quantum system is approachable. In particular, relaxation to the thermalized state depends on coupling strength, in the presence of quantum fluctuations. We also study the connection of the Wigner function thermalization to the well-known Eigenstate Thermalization.

报告人简介：Shile Chen, 现任清华大学博士后研究员。她于2023年在清华大学取得博士学位，导师为庄鹏飞老师。她的研究兴趣包括在重离子对撞中的重味物理、热化过程、以及流体力学初始条件等问题。