Gravitational potential evolution in Unified Dark Matter Scalar Field   Cosmologies: an analytical approach
  We investigate the time evolution of the gravitational potential Phi for a special class of non-adiabatic Unified Dark matter Models described by scalar field lagrangians. These models predict the same background evolution as in the LambdaCDM and possess a non-vanishing speed of sound. We provide a very accurate approximation of Phi, valid after the recombination epoch, in the form of a Bessel function of the first kind. This approximation may be useful for a future deeper analysis of Unified Dark Matter scalar field models. 
Oliver F. Piattella and Daniele Bertacca
astro-ph.CO gr-qc