Spontaneous proton decay and the origin of Peccei-Quinn symmetry

Understand

We propose a new interpretation of Peccei-Quinn symmetry within the Standard Model, identifying it with the axial $B + L$ symmetry i.e.

• $U(1)_{PQ} \equiv U(1)_{\gamma_5(B+L)}$.
• This new interpretation retains all the attractive features of Peccei-Quinn solution to strong CP problem but in addition also leads to several other new and interesting consequences.
• Owing to the identification $U(1)_{PQ} \equiv U(1)_{\gamma_5(B+L)}$ the axion also behaves like Majoron inducing small seesaw masses for neutrinos after spontaneous symmetry breaking.