W-LIKE MAPS WITH VARIOUS INSTABILITIES OF ACIM'S
This paper generalizes the results of [Li et al., 2011] and then provides an interesting example. We construct a family of W-like maps {Wa} with a turning fixed point having slope s1 on one side and –s2 on the other. Each Wa has an absolutely continuous invariant measure μa. Depending on whether [Formula: see text] is larger, equal or smaller than 1, we show that the limit of μa is a singular measure, a combination of singular and absolutely continuous measure or an absolutely continuous measure, respectively. It is known that the invariant density of a single piecewise expanding map has a positive lower bound on its support. In Sec. 4 we give an example showing that in general, for a family of piecewise expanding maps with slopes larger than 2 in modulus and converging to a piecewise expanding map, their invariant densities do not necessarily have a uniform positive lower bound on the support.