Interacting monomer-dimer model with infinitely many absorbing states

We study a modified version of the interacting monomer-dimer (IMD) model that has infinitely many absorbing (IMA) states. Unlike previously studied models with IMA states, the absorbing states can be divided into two equivalent groups which are dynamically separated infinitely far apart. Monte Carlo simulations show that this model belongs to a directed Ising universality class like the ordinary IMD model with two equivalent absorbing states. To our knowledge, this model is the first model with IMA states which does not belong to the directed percolation (DP) universality class. The DP universality class can be restored in two ways, i.e., by connecting the two equivalent groups dynamically, or by introducing a symmetry-breaking field between the two groups.