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arXiv 2103.15665hep-phhep-thnucl-th
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强磁场作用下手征夸克凝聚的非平衡动力学

Nonequilibrium Dynamics of the Chiral Quark Condensate under a Strong Magnetic Field

Gastao Krein, Carlisson Miller

摘要:

强磁场在几种情况下会影响量子色动力学(QCD)的性质,例如早期宇宙、磁星和重离子碰撞。这些例子有一个共同的特点:时间演化。强磁场影响下的QCD的一个显著性质是夸克凝聚,它是高温夸克胶子相和低温强子相之间QCD跃迁的近似序参量。我们利用夸克的线性西格玛模型研究了强磁场作用下夸克凝聚态的时间演化。我们利用非平衡量子场论的闭合时间路径理论,对夸克进行积分,得到凝聚体的平均场朗之万方程。朗之万方程的特点是耗散和噪声内核控制的阻尼系数。计算了相对论重离子碰撞中磁场和温度的阻尼系数,并求解了温度猝灭情形下的朗之万方程。与零场情况相比,磁场通过增加阻尼系数来改变耗散和噪声模式。增加的阻尼系数增加了控制凝聚态短时间演化的涨落和时间尺度,这一特征可以影响QCD跃迁时强子的形成。这里开发的形式主义可以扩展到包括其他序参量,流体动力学模式,和系统的扩展,以解决磁场的影响,在复杂的设置为重离子碰撞,早期宇宙,磁星。

英文摘要:

Strong magnetic fields impact quantum-chromodynamics (QCD) properties in several situations; examples include the early universe, magnetars, and heavy-ion collisions. These examples share a common trait: time evolution. A prominent QCD property impacted by a strong magnetic field is the quark condensate, an approximate order parameter of the QCD transition between a high-temperature quark-gluon phase and a low-temperature hadronic phase. We use the linear sigma model with quarks to address the quark condensate time evolution under a strong magnetic field. We use the closed time path formalism of nonequilibrium quantum field theory to integrate out the quarks and obtain a mean-field Langevin equation for the condensate. The Langevin equation features dissipation and noise kernels controlled by a damping coefficient. We compute the damping coefficient for magnetic field and temperature values achieved in peripheral relativistic heavy-ion collisions and solve the Langevin equation for a temperature quench scenario. The magnetic field changes the dissipation and noise pattern by increasing the damping coefficient compared to the zero-field case. An increased damping coefficient increases fluctuations and time scales controlling condensate's short-time evolution, a feature that can impact hadron formation at the QCD transition. The formalism developed here can be extended to include other order parameters, hydrodynamic modes, and system's expansion to address magnetic field effects in complex settings as heavy-ion collisions, the early universe, and magnetars.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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