θ-Vacuum : Phase Transitions and/or Symmetry Breaking at θ = π

概要

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Assuming that a quantum field theory with a θ-Vacuum term in the action shows non-trivial θ-dependence and provided that some reasonable properties of the probability distribution function of the order parameter hold, we argue that the theory either breaks spontaneously CF at θ = π or shows a singular behavior at some critical θ_c between O and π. This result, which applies to any model with a pure imaginary contribution to the euclidean action consisting in a quantized charge coppled to a phase, as QCD, is illustrated with two simple examples; one of them intimately related to Witten's result on SU(N) in the large N limit.
理論物理学刊行会の論文
2003-05-25