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Rotor Spectra, Berry Phases, and Monopole Fields: from Antiferromagnets to QCD

S. Chandrasekharan·F. -J. Jiang·M. Pepe·U. -J. Wiese
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Abstract

The order parameter of a finite system with a spontaneously broken continuous global symmetry acts as a quantum mechanical rotor. Both antiferromagnets with a spontaneously broken $SU(2)_s$ spin symmetry and massless QCD with a broken $SU(2)_L \times SU(2)_R$ chiral symmetry have rotor spectra when considered in a finite volume. When an electron or hole is doped into an antiferromagnet or when a nucleon is propagating through the QCD vacuum, a Berry phase arises from a monopole field and the angular momentum of the rotor is quantized in half-integer units.

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S. Chandrasekharan, F. -J. Jiang, M. Pepe, U. -J. Wiese. 2006-12-11. Rotor Spectra, Berry Phases, and Monopole Fields: from Antiferromagnets to QCD. https://doi.org/10.1103/physrevd.78.077901

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