ON THE NEWTONIAN COSMOLOGY EQUATIONS WITH PRESSURE

The basic equations describing a Newtonian universe with uniform press ure are reexamined. We argue that in the semi-classical formulation ad opted in the literature the continuity equation has a misleading press ure gradient term. When this term is removed, the resulting equations give the same homogeneous background solutions with pressure and the s ame long-wavelength growing mode solution for the density contrast as are obtained using the full relativistic approach.