On intrinsic ergodicity of factors of ${\mathbb{Z}}^d$ subshifts

Abstract

It is well-known that any $\mathbb{Z}$ subshift with the specification property has the property that every factor is intrinsically ergodic, i.e., every factor has a unique factor of maximal entropy. In recent work, other $\mathbb{Z}$ subshifts have been shown to possess this property as well, including $\beta$-shifts and a class of $S$-gap shifts. We give two results that show that the situation for ${\mathbb{Z}}^d$ subshifts with $d>1$ is quite different. First, for any $d>1$, we show that any ${\mathbb{Z}}^d$ subshift possessing a certain mixing property must have a factor with positive entropy which is not intrinsically ergodic. In particular, this shows that for $d>1$, ${\mathbb{Z}}^d$ subshifts with specification cannot have all factors intrinsically ergodic. We also give an example of a ${\mathbb{Z}}^2$ shift of finite type, introduced by Hochman, which is not even topologically mixing, but for which every positive entropy factor is intrinsically ergodic.

22 pages, 6 figures

References in corpus (1)

• Intrinsic ergodicity beyond specification: beta-shifts, S-gap shifts, and their factors