Structure Formation and Backreaction in Growing Neutrino Quintessence

Abstract: A dependence of the neutrino masses on the dark energy scalar field could provide a solution to the why now problem of dark energy. The dynamics of the resulting cosmological model, growing neutrino quintessence, include an attractive force between neutrinos substantially stronger than gravity. We present a comprehensive approach towards an understanding of the full cosmological evolution including the formation of large-scale neutrino structures. Important effects we account for are local variations in the dark energy and the backreaction on the background evolution, as well as relativistic neutrino velocities. For this aim, we develop a relativistic N-body treatment of the neutrinos combined with an explicit computation of the local quintessence field. At its current stage, the simulation method is successful until z ~ 1 and reveals a rich phenomenology. We obtain a detailed picture of the formation of large-scale neutrino structures and their influence on the evolution of matter, dark energy, and the late-time expansion of the universe.