Extracting invariant of conjugacy from independence entropy

The concept of independence entropy for symbolic dynamical systems was introduced in [LMP13]. This notion of entropy measures the extent to which one can freely insert symbols in positions without violating the constraints defined by the shift space. Independence entropy is not invariant under topological conjugacy. We define an invariant version of the independence entropy by setting sup h_{ind}(X) = sup{h_{ind}(Y )|Y ' X}. This invariant is bounded above by the topological entropy. We prove that equality sup h_{ind}(X) = h(X) holds for all sofic shift spaces over Z, then we give an example showing that equality does not hold for general shift spaces.