Spontaneous CP violation and the strong CP problem

TL;DR

This paper proposes a class of models with spontaneous CP violation that naturally solve the strong CP problem, predicts specific experimental signatures, and can be embedded in warped extra dimension frameworks.

Contribution

It derives conditions for solving the strong CP problem via spontaneous CP violation and introduces models that satisfy these, including warped extra dimension realizations.

Findings

Dominant topological angle contribution at 3-loop order

Models predict flavor violation and vector-like quarks

Framework addresses the Planck-TeV hierarchy

Abstract

We derive sufficient conditions that guarantee a robust solution of the strong CP problem in theories with spontaneous CP violation, and introduce a class of models satisfying these requirements. In the simplest scenarios the dominant contribution to the topological angle arises at 3-loop order in the Yukawa couplings. A variety of realizations are possible on a warped extra dimension, which can simultaneously address the Planck-TeV hierarchy. Experimental signatures of this approach to the strong CP problem include flavor violation and vector-like partners of the top or bottom quarks.