Strong CP Problem · θ̄ the vacuum angle
unseel.com · QCD θ̄ · neutron EDM · the axion fix
θ̄ dial
bound |θ̄| ≲ 10⁻¹⁰
phase
θ̄ dial (0 → 2π)
Neutron + EDM
Measured bound
Axion potential
Unseel.com · The Strong CP Problem