Branching annihilating random walks with long-range attraction in one dimension

We introduce and numerically study the branching annihilating random walks with long-range attraction (BAWL). The long-range attraction makes hopping biased in such a manner that particle's hopping along the direction to the nearest particle has larger transition rate than hopping against the direction. Still, unlike the Levy flight, a particle only hops to one of its nearest-neighbor sites. The strength of bias takes the form x(-sigma) with non-negative sigma, where x is the distance to the nearest particle from a particle to hop. By extensive Monte Carlo simulations, we show that the critical decay exponent delta varies continuously with sigma up to sigma = 1 and delta is the same as the critical decay exponent of the directed Ising (DI) universality class for sigma >= 1. Investigating the behavior of the density in the absorbing phase, we argue that sigma = 1 is indeed the threshold that separates the DI and non-DI critical behavior. We also show by Monte Carlo simulations that branching bias with symmetric hopping exhibits the same critical behavior as the BAWL.