On the holographic bound in Newtonian cosmology

The holographic principle sets an upper bound on the total entropy content of the Universe. Within the limits of a Newtonian approximation, a quantum-mechanical model is presented to describe the cosmological fluid. Under the assumption that gravitational equipotential surfaces can be identified with isoentropic surfaces, this model allows for a simple computation of the gravitational entropy of the Universe. The results thus obtained no longer saturate the holographic bound, thus representing a considerable improvement on previous theoretical estimates.