Entropy and domination for quasi-Hitchin representations

Abstract

Let $S$ be a closed oriented surface of genus $g\ge 2$. We consider an $n$-pleated representation $\rho :{\pi }_1(S)\to {\mathrm{PSL}}_n(\mathbb{C})$ obtained by bending a Hitchin representation ${\rho }_0:{\pi }_1(S)\to {\mathrm{PSL}}_n(\mathbb{R})$ along a maximal geodesic lamination. The space of such $n$-pleated representations was recently introduced by Maloni-Martone-Mazzoli-Zhang who provided a parametrization via shear-bend cocycles. Our main result is that ${\rho }_0$ dominates $\rho$ in the Hilbert length spectrum and the translation-length spectrum, with a strict domination for $\text{most}$ curves, that we call $\text{statistical}$ domination. Using this, we prove some entropy rigidity results: namely, the Hilbert entropy of any quasi-Hitchin representation in the bending fiber is strictly greater than that of ${\rho }_0$, the same for the translation length entropy when ${\rho }_0$ is $n$-Fuchsian, and in the latter case a new proof that for hyperconvex representations the Hausdorff dimension of the full limit set increases. The proof involves analyzing the weighted planar networks for finite approximants of the monodromy matrix, and establishing a strict matrix domination for generic monodromy using the equidistribution of closed geodesics in the unit tangent bundle of $S$.

49 pages, 6 figures. v2 has various minor improvements and organizational changes