Analyticity of the Hausdorff dimension and metric structures on Misiurewicz families of polynomials

Abstract

Consider a holomorphic family $(f_\lambda)_{\lambda \in \Lambda}$ of polynomial maps on $\mathbb C$ with the property that a critical point of $f_\lambda$ is persistently preperiodic to a repelling periodic point of $f_\lambda$. Let $\Omega$ be a bounded stable component of $\Lambda$ with the property that, for all $\lambda \in \Omega$, all the other critical points of $f_\lambda$ belong to attracting basins. In this paper, we introduce a dynamically meaningful geometry on $\Omega$ by constructing a natural path metric on $\Omega$ coming from a 2-form $\langle \cdot, \cdot \rangle_G$. Our construction uses thermodynamic formalism. A key ingredient is the spectral gap of adapted transfer operators on suitable Banach spaces, which also implies the analyticity of $\langle \cdot, \cdot \rangle_G$ on the unit tangent bundle of $\Omega$. As part of our construction, we recover a result of Skorulski and Urba\'nski stating that the Hausdorff dimension of the Julia set of $f_\lambda$ varies analytically over $\Omega$.