(Pseudo)Real Vacua

Preprint number: CP3-Origins-2014-28 DNRF90 and DIAS-2014-28
Author: Thomas Ryttov (CP3-Origins & DIAS)
External link: arXiv.org

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We study the alignment of the vacuum in fermionic gauge theories with enhanced global symmetries by adding a small explicit mass term. Specifically we center our investigations around the theories with two Dirac fermions in a real or pseudoreal representation of the gauge group. We find that as we vary the explicit fermion masses mU and mD there are critical points where the system makes a discontinuous jump from one vacuum to another. This occurs when one of the fermion masses vanish. Hence there are four unique vacua depending only on the sign of mU and mD. Due to the enhanced global symmetry nothing is therefore expected to happen at the point mU=−mD where, on the other hand, theories with fermions in a complex representation of the gauge group are expected to develop a CP violating (Dashen) phase.