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The Strong CP Problem, String Theory and the Nelson-Barr Mechanism

R. G. Leigh
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Abstract

We review recent work on the strong CP problem in the context of realistic string-inspired models. We discuss the various solutions, review the conjecture that CP is generally a gauged discrete symmetry in string theory and then consider models of the Nelson-Barr type. We note that squark non-degeneracy spoils the Nelson-Barr structure at the one loop level. We stress that string theory expectations, as well as naturalness arguments, make it very difficult to avoid the constraints on non-degeneracy.

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R. G. Leigh. 1993-07-02. The Strong CP Problem, String Theory and the Nelson-Barr Mechanism. https://arxiv.org/abs/hep-ph/9307214

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