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

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 $λϕ^4$ 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. As a result, in the true vacuum, the field acquires non zero mass proportional to the energy density of massive neutrino matter and could give rise to late-time cosmic acceleration. We also address the issues related to stability of self coupling under radiative corrections.

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