Probing Long-Range Force Between Neutrinos from Cosmic Structures

The long-range force between neutrinos is poorly constrained. In the late-time universe, a long-range force that is a few orders of magnitude stronger than gravity can induce Jeans perturbation instability in the non-relativistic cosmic neutrino background, drastically changing its large-scale behavior. In this talk, I will describe how the cosmic neutrino background evolves and forms nonlinear bound states in the presence of a long-range force. I will then discuss the impact of these neutrino bound states on the matter structures in the universe, and the constraints due to the absence of these signals.