On Coupled Directed Percolation Processes: A Unifying View

It is shown that the universal critical properties of two recently introduced coupled directed percolation processes can be described by a single rapidity reversal invariant stochastic reaction-diffusion model. It is demonstrated that all renormalizations needed for the calculation of the universal scaling behavior near the multicritical point can be gained from the Gribov process (Reggeon field theory). Consequently the crossover exponent describing the scaling of the linear coupling parameter is given by Phi = 1 to all orders of the perturbation expansion.