Speaker
Description
We propose a solution to the strong CP problem that specifically relies on massless quarks and has no light axion. The QCD color group $SU(3)_c$ is embedded into a larger, simple gauge group (grand-color) where one of the massless, colored fermions enjoys an anomalous chiral symmetry, rendering the strong CP phase unphysical. The grand-color gauge group $G_{\rm GC}$ is Higgsed down to $SU(3)_c\times G_{c'}$, after which $G_{c'}$ eventually confines at lower energy, spontaneously breaking the chiral symmetry and generating a real, positive mass to the massless, colored fermion. Since the chiral symmetry has a $G_{c'}$ anomaly, there is no corresponding light Nambu-Goldstone boson. Potential experimental signals of our mechanism include vector-like quarks, pseudo Nambu-Goldstone bosons, light dark matter decay, and primordial gravitational waves from the new strong dynamics.
