The quintessence field coupled to the cosmic neutrino background (CNB) has been widely discussed as an alternative mechanism to address the coincidence problem. As it is well known, it is possible to extend such models to obtain quintessential inflation, that is, to incorporate inflationary stage as well. Taking an alternative route, one can start from the well-established inflationary models and obtain successful quintessence models at the expense of coupling with the CNB. To follow this route, we use a slightly reformulated model addressed in [H. Mohseni Sadjadi and V. Anari, Phys Rev. D 95, 123521 (2017)]. This particular model assumes ${\mathcal{Z}}_2$ symmetry for both scalar field potential and coupling term, which then breaks down in course of the cosmological evolution. For our discussion, however, the ${\mathcal{Z}}_2$ symmetry of the potential is not mandatory for the model to work. The conventional mechanism of particle production by the oscillating inflaton field (and their subsequent thermalization) remains operative. It is plain to see that the proposed construction can be easily applied for many successful models of inflation to incorporate dark energy at the expense of coupling with the CNB. We address the issue of neutrino nuggets from the quantum field theory point of view. Namely, these nuggets are considered as bound states caused basically by the Yukawa force, which arises in the framework of linear perturbation theory due to exchange of virtual quanta of quintessence field between the neutrinos.

• Received 13 February 2021
• Accepted 11 March 2021

DOI:https://doi.org/10.1103/PhysRevD.103.063540