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

Abstract

Let $f$ be an endomorphism of $\mathbb{CP}^k$ and $ν$ be an $f$-invariant measure with positive Lyapunov exponents $(λ_1,\...,λ_k)$. We prove a lower bound for the pointwise dimension of $ν$ in terms of the degree of $f$, the exponents of $ν$ and the entropy of $ν$. In particular our result can be applied for the maximal entropy measure $μ$. When $k=2$, it implies that the Hausdorff dimension of $μ$ is estimated by $\dim_{\cal H} μ\geq {\log d \over λ_1} + {\log d \over λ_2}$, which is half of the conjectured formula. Our method for proving these results consists in studying the distribution of the $ν$-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 $ν$-generic inverse branches of $f^n$.