Consistency analysis of a Dark Matter velocity dependent force as an alternative to the Cosmological Constant

TL;DR

This paper investigates an alternative dark matter model with velocity-dependent forces to explain cosmic acceleration, finding that a force proportional to velocity squared can mimic effects of a cosmological constant.

Contribution

It introduces and tests a velocity-squared dependent force model as an alternative to the cosmological constant using numerical simulations.

Findings

Models with force proportional to velocity or higher powers cannot mimic acceleration.

Force proportional to velocity squared remains consistent with accelerated expansion.

The model offers a potential alternative explanation for cosmic acceleration.

Abstract

A range of cosmological observations demonstrate an accelerated expansion of the Universe, and the most likely explanation of this phenomenon is a cosmological constant. Given the importance of understanding the underlying physics, it is relevant to investigate alternative models. This article uses numerical simulations to test the consistency of one such alternative model. Specifically, this model has no cosmological constant, instead the dark matter particles have an extra force proportional to velocity squared, somewhat reminiscent of the magnetic force in electrodynamics. The constant strength of the force is the only free parameter. Since bottom-up structure formation creates cosmological structures whose internal velocity dispersions increase in time, this model may mimic the temporal evolution of the effect from a cosmological constant. It is shown that models with force linearly proportional to internal velocites, or models proportional to velocity to power three or more cannot mimic the accelerated expansion induced by a cosmological constant. However, models proportional to velocity squared are still consistent with the temporal evolution of a Universe with a cosmological model.