Dark Matter Gravitational Clustering With a Long-Range Scalar   Interaction
  We explore the possibility of improving the $\Lambda$CDM model at megaparsec scales by introducing a scalar interaction which increases the mutual gravitational attraction of dark matter particles. Using N-body simulations, we study the spatial distribution of dark matter particles and halos. We measure the effect of modifications in the Newton's gravity on properties of the two-point correlation function, the dark matter power spectrum, the cumulative halo mass function and density probability distribution functions. The results look promising: the scalar interactions produce desirable features at megaparsec scales without spoiling the $\Lambda$CDM successes at larger scales. 
Wojciech A. Hellwing, Roman Juszkiewicz