  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.
