On the dimension of invariant measures of endomorphisms of $\mathbb{CP}^k$

Christophe Dupont

Published 2008-09-16, updated 2010-04-13Version 3

Let $f$ be an endomorphism of $\mathbb{CP}^k$ and $\nu$ be an $f$-invariant measure with positive Lyapunov exponents $(\lambda_1,\...,\lambda_k)$. We prove a lower bound for the pointwise dimension of $\nu$ in terms of the degree of $f$, the exponents of $\nu$ and the entropy of $\nu$. In particular our result can be applied for the maximal entropy measure $\mu$. When $k=2$, it implies that the Hausdorff dimension of $\mu$ is estimated by $\dim_{\cal H} \mu \geq {\log d \over \lambda_1} + {\log d \over \lambda_2}$, which is half of the conjectured formula. Our method for proving these results consists in studying the distribution of the $\nu$-generic inverse branches of $f^n$ in $\mathbb{CP}^k$. Our tools are a volume growth estimate for the bounded holomorphic polydiscs in $\mathbb{CP}^k$ and a normalization theorem for the $\nu$-generic inverse branches of $f^n$.