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Title:Quasiconformal mappings on planar surfaces
Author(s):Ackermann, Colleen Teresa
Director of Research:Hinkkanen, Aimo; Tyson, Jeremy
Doctoral Committee Chair(s):Wu, Jang-Mei
Doctoral Committee Member(s):Nikolaev, Igor
Department / Program:Mathematics
Discipline:Mathematics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):quasiconformal mapping
Grushin plane
Abstract:This thesis discusses three different projects concerning quasiconformal mappings on planar surfaces. In the first two projects we show that a priori weaker conditions still suffice to prove quasiconformality. The geometric definition states that an orientation-preserving homeomorphism f:U → f(U) is quasiconformal if there exists K ≥ 1 such that for all Q, Q ⊂ U the ratio of the modulus of f(Q) to the modulus of Q is bounded above by K. We show that for the subclass of homeomorphisms that preserves the set of vertical lines, it suffices to just consider squares with sides parallel to the coordinate axes and at forty-five degree angles to the coordinate axes. Another more recent sufficient condition for quasiconformality discovered by Hubbard in 2006, requires that the skews of triangles be only distorted by a bounded amount. Haïssinsky, Hinkkanen and I proved that if there exists a constant K such that (f(T)) ≤ K for all equilateral triangles T, then f is quasiconformal. Furthermore, this condition is also sufficient for mappings between finite-dimensional Hilbert spaces. In the last project we study quasiconformal mappings on a generalized class of Grushin planes. We define quasisymmetries between these Grushin planes and the complex plane, and use them to find a Grushin Beltrami equation and state an analytic definition of quasisymmetry on the Grushin plane. Finally we look at a previously discovered class of conformal mappings on the Grushin plane, and show that these conformal mappings agree with our analytic definition of quasisymmetry in the conformal case.
Issue Date:2016-04-22
Type:Thesis
URI:http://hdl.handle.net/2142/90613
Rights Information:Copyright 2016 Colleen Ackermann
Date Available in IDEALS:2016-07-07
Date Deposited:2016-05


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