High-resolution cosmological simulations of primordial dark matter clustering under long-range and fractional forces

Abstract

Long-range attractive fifth forces can lead to exponential instabilities in the early Universe. For fermions with a Yukawa coupling to a sufficiently light scalar mediator, rapid oscillations of the scalar field can lead to a conservative force law with fractional behaviour on sufficiently large scales. We study cosmological systems evolving under both this fractional potential and the Newtonian potential using high-resolution N-body simulations. We find that, at the same mass scale, halos that form under the fractional potential are much more dense than those that from the Newtonian potential. However, we also find that the perturbed scalar field may have large fluctuations once halo sizes become comparable to an effective Compton length, which will modify subsequent clustering and collapse.