Finite-time collapse process and non-local correlations are incompatible with non-signaling theories

We propose a hidden variable analysis of collapse dynamics in which the state's reduction process may take a finite time $\delta t$. A full characterization of the model is given for the case of black boxes. By introducing nonlocal perfect correlations to a two black-boxes scenario, it is shown that in order to avoid faster than light communication, the reduction time associated to the system must be strictly null. Furthermore we prove that the result above holds even when there is a time window between the choice of both part's inputs. Our results represent a new evidence of the instantaneous nature of the wave function collapse process which could have implications in foundations of quantum mechanics and information science.