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摘要: 在有时空结构的非平衡定常态上,由于对称性的自发破缺,形成非零能、带耗散的Goldstone模。本文以么模激光的饱和状态为例,从普遍的相位对称性出发,应用闭路格林函数中的Ward-Takahashi恒等式,具体地导出了这种带耗散的推广的Goldstone定理的一个形式,讨论了相应的Goldstone模式的物理意义。求得了饱和状态光量子态的分裂。具体给出了状态从相位有序→相位无序的转化规律,从而给自发破缺的对称性的恢复一个具体的描述。
Abstract: In consequence of the spontaneous symmetry breaking, non-zero energy Goldstone, modes with dissipation are excited in a non-equilibrium stationary state with space-time structure. In this paper, as a specific example, the Ward-Takahashi identities formulated in the close time path Green's function method is applied to the saturation state of a single mode laser. A generalized Goldstone theorem in a weak inho-mogeneous dissipative system is established and the physical interpretation of the Goldstone mode is discussed. As a result of the Goldstone theorem, the pole in the Green's function of the laser light splits into two with equal weights, each corresponding to a quanta with the same frequency but different dissipation. Together with the order parameter (the average value of the vector potential), these two kinds of quanta (one of which is the Goldstone mode) give a complete description of the order-disorder transition of the phase symmetry in the saturation state of the laser. A detailed discussion on the restoration of the spontaneously broken symmtry of the phase is given.