Spherical `Top-Hat' Collapse in general Chaplygin gas dominated   universes
  We expand previous works on the spherical `top-hat' collapse (SC-TH) framework in generalized Chaplygin gas (gCg) dominated universes. Here we allow the collapse in all energetic components within the system. We analyze the non-linear stages of collapse for various choices of parameter \alpha of the gCg model introducing an exact formulation for the so-called effective sound speed, $c_{eff}^2$. We show that, within the SC-TH framework, the growth of the structure becomes faster with increasing values of \alpha. 
R. A. A. Fernandes, J. P. M. de Carvalho, A. Yu. Kamenshchik, U.   Moschella, A. da Silva
astro-ph.CO