Bratteli-Vershik representations of some one-sided substitution subshifts

Reem Yassawi

Published 2009-07-16, updated 2010-12-14Version 3

We study one-sided substitution subshifts, and how they can be represented using Bratteli-Vershik systems. In particular we focus on minimal recognizable substitutions such that the generated one-sided substitution subshift contains only one non-shift-invertible element (a branch point), and we call these substitutions quasi-invertible. We give an algorithm to check whether a substitution is quasi-invertible, and show that any substitution with a rational Perron value is orbit equivalent to a quasi-invertible substitution. If the quasi-invertible substitution is left proper, then its subshift is equal to a substitution subshift where the original branch point is the new substitution fixed point. We use these results to prove that any reasonable quasi-invertible substitution subshift has a Bratteli-Vershik representation. We also give an example of a pair of substitutions whose 2-sided subshifts are topologically conjugate, while their 1-sided subshifts are not.