Yet another characterization of the Pisot substitution conjecture

Abstract

We give a sufficient geometric condition for a subshift to be measurably isomorphic to a domain exchange and to a translation on a torus. And for an irreducible unit Pisot substitution, we introduce a new topology on the discrete line and we give a simple necessary and sufficient condition for the symbolic system to have pure discrete spectrum. This condition gives rise to an algorithm based on computation of automata. To see the power of this criterion, we provide families of substitutions that satisfies the Pisot substitution conjecture: 1) $a \mapsto a^kbc$, $b \mapsto c$, $c \mapsto a$, for $k \in \mathbb{N}$ and 2) $a \mapsto a^lba^{k-l}$, $b \mapsto c$, $c \mapsto a$, for $k \in \mathbb{N}_{\geq 1}$, for $0 \leq l \leq k$ using different methods. And we also provide an example of $\mathcal{S}$-adic system with pure discrete spectrum everywhere.