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Study of CP(N-1) θ-Vacua by Cluster-Simulation of SU(N) Quantum Spin Ladders

B. B. Beard·M. Pepe·S. Riederer·U. J. Wiese
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Abstract

D-theory provides an alternative lattice regularization of the (1+1)-d CP(N-1) quantum field theory. In this formulation the continuous classical CP(N-1) fields emerge from the dimensional reduction of discrete SU(N) quantum spins. In analogy to Haldane's conjecture, ladders consisting of an even number of transversely coupled spin chains lead to a CP(N-1) model with vacuum angle θ= 0, while an odd number of chains yields θ= π. In contrast to Wilson's formulation of lattice field theory, in D-theory no sign problem arises at θ= π, and an efficient cluster algorithm is used to investigate the θ-vacuum effects. At θ= πthere is a first order phase transition with spontaneous breaking of charge conjugation symmetry for CP(N-1) models with N>2.

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B. B. Beard, M. Pepe, S. Riederer, U. J. Wiese. 2004-06-30. Study of CP(N-1) θ-Vacua by Cluster-Simulation of SU(N) Quantum Spin Ladders. https://doi.org/10.1103/physrevlett.94.010603

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