On automorphism groups of Toeplitz subshifts

In this article we study automorphisms of Toeplitz subshifts. Such groups are abelian and any finitely generated torsion subgroup is finite and cyclic. When the complexity is non superlinear, we prove that the automorphism group is, modulo a finite cyclic group, generated by a unique root of the shift. In the subquadratic complexity case, we show that the automorphism group modulo the torsion is generated by the roots of the shift map and that the result of the non superlinear case is optimal. Namely, for any $\varepsilon > 0$ we construct examples of minimal Toeplitz subshifts with complexity bounded by $C n^{1+\epsilon}$ whose automorphism groups are not finitely generated. Finally, we observe the coalescence and the automorphism group give no restriction on the complexity since we provide a family of coalescent Toeplitz subshifts with positive entropy such that their automorphism groups are arbitrary finitely generated infinite abelian groups with cyclic torsion subgroup (eventually restricted to powers of the shift)

The mathematical research of William Parry FRS

In this article we survey the mathematical research of the late William (Bill) Parry, FRS

A certain synchronizing property of subshifts and flow equivalence

We will study a certain synchronizing property of subshifts called $\lambda$-synchronization. The $\lambda$-synchronizing subshifts form a large class of irreducible subshifts containing irreducible sofic shifts. We prove that the $\lambda$-synchronization is invariant under flow equivalence of subshifts. The $\lambda$-synchronizing K-groups and the $\lambda$-synchronizing Bowen-Franks groups are studied and proved to be invariant under flow equivalence of $\lambda$-synchronizing subshifts. They are new flow equivalence invariants for $\lambda$-synchronizing subshifts.Comment: 28 page