N-Body Simulations for Coupled Scalar Field Cosmology
  We describe in detail the general methodology and numerical implementation of
consistent N-body simulations for coupled scalar field cosmological models,
including the background cosmology and the generation of initial conditions
(with the different couplings to different matter species taken into account).
We perform fully consistent simulations for a class of coupled scalar field
models with an inverse power-law potential and negative coupling constant, for
which the chameleon mechanism does not operate. We find that in such
cosmological models the scalar-field potential plays a negligible role except
in the background expansion, and the fifth force that is produced is
proportional to gravity in magnitude, justifying the use of a rescaled
gravitational constant G in some earlier N-body simulations of similar models.
We study the effects of the scalar coupling on the nonlinear matter power
spectra and compare with linear perturbation calculations to investigate where
the nonlinear model deviates from the linear approximation. For the first time,
the algorithm to identify gravitationally virialized matter halos is adapted to
the scalar field cosmology, and then used to measure the mass function and
study the properties of virialized halos. We find that the net effect of the
scalar coupling helps produce more heavy halos in our simulation boxes and
suppresses the inner (but not the outer) density profile of halos compared with
those predicted by lambda-CDM, while this suppression weakens as the coupling
between the scalar field and dark matter particles increases in strength.
