Introducing DASEP: the doubly asymmetric simple exclusion process

Research in combinatorics has often explored the asymmetric simple exclusion process (ASEP). The ASEP, inspired by examples from statistical mechanics, involves particles of various species moving around a lattice. With the traditional ASEP particles of a given species can move but do not change species. In this paper a new combinatorial formalism, the DASEP (doubly asymmetric simple exclusion process), is explored. The DASEP is inspired by biological processes where, unlike the ASEP, the particles can change from one species to another. The combinatorics of the DASEP on a one dimensional lattice are explored, including the associated generating function. The stationary probabilities of the DASEP are explored, and results are proven relating these stationary probabilities to those of the simpler ASEP.Comment: For review for special issue of "S\'eminaire Lotharingien de Combinatoire" devoted to lattice path