Regularity of Lyapunov exponents at one-point Lyapunov spectra: the semisimple case

We study the regularity of Lyapunov exponents as functions on the space of compactly supported probability measures on $\mathrm{G}\mathrm{L}(d,\mathbb{R})$. We prove that the Lyapunov exponents are pointwise log-Hölder continuous with respect to the Wasserstein distance, at semisimple probability measures with one-point Lyapunov spectrum. The proof relies on a decomposition of the action into virtually conformal subspaces and a Berry-Esseen type estimate for the random walk towards these subspaces.