Exact and Truncated Dynamics in Nonequilibrium Field Theory
Exact and Truncated Dynamics in Nonequilibrium Field Theory
复制标题
非平衡场论中的精确和截断动力学
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
C. Wetterich
中科院分区：
文献类型：
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作者：
G. Aarts;G. Bonini;C. Wetterich
非微扰动力学的量子场的平衡往往是描述的时间演化的相关函数的层次，使用近似方法，如哈特里，大Nf，和nPI有效的行动技术。这些截断计划可以同样很好地实现在一个经典的统计系统，其中的结果可以通过比较得到的完整的非线性演化数值方法进行测试。对于1+1维标量场，我们发现早期的行为是由Hartree动力学定性再现。直接散射的包含将其提高到定量水平。我们表明，在中间时间的非热温度分布的出现可以理解的发展方程的不动点在Hartree近似。轮廓的形式明确地取决于初始系综。虽然截断的演化方程似乎无法摆脱不动点，但完整的非线性演化显示出热化和（令人惊讶的）缓慢弛豫。
Nonperturbative dynamics of quantum fields out of equilibrium is often described by the time evolution of a hierarchy of correlation functions, using approximation methods such as Hartree, large Nf, and nPI-effective action techniques. These truncation schemes can be implemented equally well in a classical statistical system, where results can be tested by comparison with the complete nonlinear evolution obtained by numerical methods. For a 1+1 dimensional scalar field we find that the early-time behaviour is reproduced qualitatively by the Hartree dynamics. The inclusion of direct scattering improves this to the quantitative level. We show that the emergence of nonthermal temperature profiles at intermediate times can be understood in terms of the fixed points of the evolution equations in the Hartree approximation. The form of the profile depends explicitly on the initial ensemble. While the truncated evolution equations do not seem to be able to get away from the fixed point, the full nonlinear evolution shows thermalization with a (surprisingly) slow relaxation.