  Dark energy is frequently modelled as an additional dynamical scalar field
component in the Universe, referred to as "quintessence", which drives the
late-time acceleration. Furthermore, the quintessence field may be coupled to
dark matter and/or baryons, leading to a fifth force. In this paper we explore
the consequences for non-linear cosmological structure formation arising from a
momentum coupling between the quintessence field and dark matter only. The
coupling leads to a modified Euler equation, which we implement in an N-body
cosmological simulation. We then analyse the effects of the coupling on the
non-linear power spectrum and the properties of the dark matter halos. We find
that, for certain quintessence potentials, a positive coupling can lead to
significantly reduced structure on small scales and somewhat enhanced structure
on large scales, as well as reduced halo density profiles and increased
velocity dispersions.

Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology