Quantum Field Theories in Strong External Fields

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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.