On the Beltrami equation, once again: 54 years later

Abstract

We prove that the quasiregular mappings given by the (normalized) principal solution of the linear Beltrami equation (1) and the principal solution of the quasilinear Beltrami equation are inverse to each other. This basic fact is deduced from the Liouville theorem for generalized analytic functions. It essentially simplifies the known proofs of the "measurable Riemann mapping theorem" and its holomorphic dependence on parameters.