Researchers have explored a connection between CP symmetry violation in the leptonic sector and the strong CP phase (θ̄) in theories with left-right symmetry and generalized parity. In these theories, the bare QCD angle is restricted to a CP-conserving value, and the physical strong-CP phase θ̄ is related to a CP-odd parity-breaking parameter, ε. The study focuses on the Dirac-neutrino realization, where imposing a sectorial reality condition on the Dirac lepton Yukawa matrices transforms observable leptonic CP violation from an independent input into a branch-dependent prediction.

Parity reconstructs the right-handed leptonic mixing matrix, while the leptonic reality condition requires it to be rephasing-equivalent to the complex conjugate of the left-handed one. For generic three-generation Yukawas, compatibility between these conditions is equivalent to the vanishing of a single Jarlskog-type CP-odd invariant. In the physical Dirac hierarchy, for fixed oscillation data, mass ordering, and discrete leptonic branch, compatibility determines the PMNS Jarlskog invariant as a function of the lightest neutrino mass and ε.

Numerical analysis shows that in compressed mixed-sign Dirac-neutrino spectra, small signed mass sums can amplify a tiny parity deformation into order-one values of the normalized PMNS Jarlskog invariant, including maximal CP violation. The corresponding quark reconstruction independently provides a calculable, branch-dependent conversion between ε and θ̄. Together, these leptonic and quark relations define a family of correlations among leptonic CP violation, the absolute neutrino mass scale, and the strong CP phase.