AbstractIn this talk we discuss a notion of $\psi$-Dirichlet in Diophantine approximation which concerns improving Dirichlet’s approximation theorem to a general approximating function $\psi$. This notion was introduced by Kleinbock and Wadleigh in 2018 and generalizes the classical notion of a matrix being Dirichlet-improvable. In particular, we prove a partial zero-one law for the Lebesgue m...
Abstract:The moduli spaces of points on n-spheres carry natural actions of braid groups. For n=0, 1, and 3, we prove that these symmetries extend to actions of mapping class groups of certain positive genus surfaces, through exceptional isomorphisms with certain moduli of local systems. Moreover, the isomorphisms map the Coxeter invariants of points on spheres to the boundary monodromy of the ...