The Ellis semigroup of bijective substitutions
Johannes Kellendonk, Reem Yassawi · Groups Geometry and Dynamics · 2021
For topological dynamical systems (X,T,\sigma) with abelian group T , which admit an equicontinuous factor \pi:(X,T,\sigma)\to (Y,T,\delta) , the Ellis semigroup E(X) is an extension of Y by its subsemigroup E^{\operatorname{fib}}(X) of elements which preserve the fibres of \pi . We establish methods to compute E^{\operatorname{fib}}(X) and use them to determine the Ellis semigroup of dynamical systems arising from primitive aperiodic bijective substitutions. As an application, we show that for these substitution shifts, the virtual automorphism group is isomorphic to the classical automorphism group.