标题： 强耦合手性相中的正电子素 显示英文标题

标题： Strongly coupled positronium in a chiral phase

摘要： 在相对论量子约束动力学框架下，研究了其赝标量部分中的强耦合正电子素。 采用Case的奇异势自伴扩张方法，该方法避免了显式引入正则化截断。 发现当耦合常数\alpha 增加时，在临界值\alpha = \alpha _c = 1/2 处，束缚态谱出现突然变化。 对于\alpha > \alpha _c，除了\alpha < \alpha _c 时存在的状态外，质量谱还显示了一组无限多个束缚态，这些束缚态集中在从质量 W=0 开始的狭窄区域内。 当\alpha 从上方趋于\alpha _c 时，这些态收缩为一个无质量态，该态与谱的其余部分之间存在质量间隙。 该态具有代表戈德斯通玻色子并标志手征对称性自发破缺的所需性质。 建议将临界耦合常数\alpha _c 视为QED中可能的紫外稳定固定点，其中存在两种相，通过一阶手征相变相互连接。 显示英文摘要

摘要： Strongly coupled positronium, considered in its pseudoscalar sector, is studied in the framework of relativistic quantum constraint dynamics. Case's method of self-adjoint extension of singular potentials, which avoids explicit introduction of regularization cut-offs, is adopted. It is found that, as the coupling constant \alpha increases, the bound state spectrum undergoes an abrupt change at the critical value \alpha = \alpha_c = 1/2. For \alpha > \alpha_c, the mass spectrum displays, in addition to the existing states for \alpha < \alpha_c, a new set of an infinite number of bound states concentrated in a narrow band starting at mass W=0. In the limit \alpha going to \alpha_c from above, these states shrink to a single massless state with a mass gap with the rest of the spectrum. This state has the required properties to represent a Goldstone boson and to signal a spontaneous breakdown of chiral symmetry. It is suggested that the critical coupling constant \alpha_c be viewed as a possible candidate for an ultra- violet stable fixed point of QED, with a distinction between two phases, joined to each other by a first-order chiral phase transition.