Extending the scope of models for large-scale structure formation in the universe

We propose a phenomenological generalization of the models of large-scale s tructure formation in the Universe by gravitational instability in two ways : we include pressure forces to model multi-streaming, and noise to model f luctuations due to neglected short-scale physical processes. We show that p ressure gives rise to a viscous-like force of the same character as the one introduced in the adhesion model, while noise leads to a roughening of the density field, yielding a scaling behavior of its correlations.