Rational maps of \(\mathbb{CP}^2\) with equal dynamical degrees,
no invariant foliation, and two distinct measures of maximal entropy
Oct. 21, 2016
noon [NEW DAY/TIME] PHG 646
Abstract
The ergodic properties of a rational map \(f\colon \mathbb{CP}^2
\longrightarrow \mathbb{CP}^2\) are tied to its dynamical degrees
\(\lambda_1(f)\) and \(\lambda_2(f)\). Maps with \(\lambda_1(f) >
\lambda_2(f)\) share many properties of the Hénon maps, having a
measure of maximal entropy of saddle type. Maps with \(\lambda_2(f) >
\lambda_1(f)\) share many properties of holomorphic endomorphisms, having a
measure of maximal entropy that is repelling. In both cases it is believed
(and often proved) that \(f\) has a unique measure of maximal entropy.
Early examples of maps with \(\lambda_1(f) = \lambda_2(f)\) were skew
products, having an invariant fibration. Guedj asked whether this happens
in general. We show that there is a simple way to produce many rational
maps of \(\mathbb{CP}^2\) with equal dynamical degrees, no invariant
foliation, and two measures of maximal entropy, one of saddle-type and one
repelling. Many of the techniques are geometric. This is joint work with
Jeff Diller and Han Liu and it builds on previous joint work with Scott
Kaschner and Rodrigo Pérez.
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Last modified: April 08 2016 - 20:30:35