Can massive neutrinos be responsible for late time phase transition $\hat{\rm a}$ {\it la} deceleration to acceleration in our Universe?

Understand

We attempt a novel mechanism to understand the underlying cause of late-time cosmic acceleration using a distinguished physical process taking place in the late Universe.

• The turning of massive neutrinos from relativistic to non-relativistic might cause a phase transition at late times.
• We implement this idea using massless $\lambda \phi^4$ theory coupled to massive neutrino matter such that the coupling is proportional to the trace of the energy-momentum tensor of neutrino matter.
• As massive neutrinos become non-relativistic, their coupling to the scalar field builds up dynamically giving rise to spontaneous symmetry breaking in the low-density regime.