Renormalization Group Flows into Phases with Broken Symmetry(Condensed Matter and Statistical Physics)

概要

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We describe a method to continue the fermionic renormalization group flow into phases with broken global symmetry. This method does not "require a Hubbard-Stratonovich decoupling of the interaction Instead an infinitesimally small symmetry-breaking component is inserted into the initial action, as an initial condition for the flow of the self-energy. Its flow is driven by the interaction, and at low scales it saturates at a nonzero value if there is a tendency for spontaneous symmetry breaking in the corresponding channel. For the reduced BCS model, we show how a small initial gap amplitude flows to the value given by the exact solution of the model. We also discuss the emergence of the Goldstone boson in this approach.
理論物理学刊行会の論文
2004-12-25