Quantum Field Theories in Strong External Fields

在该基金的资助下，我们在1995学年开展了以下三个课题的研究：1.失向手征凝聚（DCC）和强电磁场的效应：DCC涉及在强子-强子或重离子碰撞过程中，热碎片快速冷却后可能形成的具有失向手征取向的亚稳态，在这种亚稳态中，手征对称性将得到恢复。在线性sigma模型的框架下，计算了静态和均匀电磁场的单圈有效拉格朗日量。结果表明，手性取向保持不变，这是一个令人惊讶的结果。这是由于O（2）对称性未破缺的缘故，并且该结论对于时变电磁场仍然有效。结果表明，电磁场仅通过Wess-Zumino项影响DCC的形成，而Wess-Zumino项在低能有效理论水平上概括了QCD中手征反常的作用。的异常效应示出作为一个“踢”的西格玛模型场配置。Asakawaal.is提出了在模拟中实现这种效应的可能性，我们正在与他们进行接触。2.一维费米子理论的热力学Bethe分析：用热力学Bethe分析方法研究Gross-Neveu模型。通过将它与大N展开相结合，我们得到了对自由能的次领先修正。3. APEX实验的唯象分析：讨论了APEX实验组声称的峰结构的消失受到各种不确定性的影响，其中最严重的是由于使用了厚靶，正如耶鲁大学物理学家和实验组成员Jack Greenberg所批评的那样。

Under support of the Grant we carred out the research on the following three subjects as described below in the academic year 1995.1.Disoriented Chiral Condensate (DCC) and the Effect of Strong Electromagnatic Fields :DCC concernes the proposed metastable states with misaligned chiral orientation which is expected to form during the hadron-hadron or heavy ion collisions after rapid cooling of hot debris, in which the chiral symmetry would be restored. The 1-loop effective Lagrangian of the static and uniform electromagnetic fields are computed in the framework of the linear sigma model. It is shown that the chiral orientation remains unchanged, a surprising result. This is due to the unbroken O (2) symmetry and the conclusion remains valid for time-varying electromagnetic fields. It is observed that the electromagnetism affects DCC formation only through the Wess-Zumino term which summarizes the effect of chiral anomaly in QCD at the level of low-energy effective theory. The anomaly effect is shown to act as a "kick" to the sigma-model field configurations. The possibility of implementing the effect into the simulation by Asakawa et al.is suggested and we are in the process of making contact with them.2.Thermodynamics of 1-Dimensional Fermion Theories by Thermodynamic Bethe Ansatz :The Gross-Neveu model is investigated by the method of thermodynamic Bethe ansatz. By combining it with the large-N expansion we have obtained the next-to-leading correction to the free energy. It indicates that the qualitative feature of the leading-order result remains unchanged.3.Phenomenological Analysis of the APEX Experiment :It is discussed that the disappearance of the peak structure claimed by the APEX group suffers from various uncertainties whose most serious one is due to the use of thick target, as criticised by Jack Greenberg, a Yale physicist and a member of the experimental group.