Complexity of Shift Spaces on Semigroups

Abstract

Let G=⟨S|RA⟩G=⟨S|RA⟩ be a semigroup with generating set S and equivalences RARA among S determined by a matrix A. This paper investigates the complexity of G-shift spaces by yielding the Petersen–Salama entropies [defined in Petersen and Salama (Theoret Comput Sci 743:64–71, 2018)]. After revealing the existence of Petersen–Salama entropy of G-shift of finite type (G-SFT), the calculation of Petersen–Salama entropy of G-SFT is equivalent to solving a system of nonlinear recurrence equations. The complete characterization of Petersen–Salama entropies of G-SFTs on two symbols is addressed, which extends (Ban and Chang in On the topological entropy of subshifts of finite type on free semigroups, 2018. arXiv:1702.04394) in which G is a free semigroup.