QCD surprises: Strong CP problem, neutrino mass, Dark Matter and Dark Energy

An unexpected explanation for neutrino mass, Dark Matter (DM) and Dark Energy (DE) from genuine Quantum Chromodynamics (QCD) of the Standard Model (SM) is proposed here, while the strong CP problem is resolved without any need to account for fundamental axions. We suggest that the neutrino sector can be in a double phase in the Universe: i) relativistic neutrinos, belonging to the SM; ii) non-relativistic condensate of Majorana neutrinos. The condensate of neutrinos can provide an attractive alternative candidate for the DM, being in a cold coherent state. We will explain how neutrinos, combining into Cooper pairs, can form collective low-energy degrees of freedom, hence providing a strongly motivated candidate for the QCD (composite) axion. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study proposes an unexpected explanation for neutrino mass, dark matter, and dark energy. By considering the different phases of neutrinos in the universe, a candidate for dark matter in the form of a condensate of neutrinos is suggested, providing a motivated candidate for the composite axion in the context of quantum chromodynamics.