Area-minimizing properties of Pansu spheres in the sub-Riemannian 3-sphere

The authors were supported by MINECO grant MTM2017-84851-C2-1-P and Junta de Andaluc´ıa grants A-FQM-441-UGR18 and FQM325.We consider the sub-Riemannian 3- sphere (S-3, gh) obtained by restriction of the Riemannian metric of constant curvature 1 to the planar distribution orthogonal to the vertical Hopf vector field. It was shown in [A. Hurtado and C. Rosales, Area-stationary surfaces inside the sub-Riemannian three-sphere, Math. Ann. 340 (2008), no. 3, 675-708] that (S-3, g(h)) contains a family of spherical surfaces {S-lambda}(lambda >= 0) with constant mean curvature.. In this work, we first prove that the two closed half-spheres of S-0 with boundary C-0 = {0} x S-1 minimize the sub-Riemannian area among compact C-1 surfaces with the same boundary. We also see that the only C-2 solutions to this Plateau problem are vertical translations of such half-spheres. Second, we establish that the closed 3-ball enclosed by a sphere S-lambda with lambda > 0 uniquely solves the isoperimetric problem in (S-3, g(h)) for C-1 sets inside a vertical solid tube and containing a horizontal section of the tube. The proofs mainly rely on calibration arguments.MINECO grant MTM2017-84851-C2-1-PJunta de Andaluc´ıa grants A-FQM-441-UGR18 and FQM32

Complete noncompact CMC surfaces in hyperbolic 3-space

In this thesis we study the asymptotic Plateau problem for surfaces with constant mean curvature (CMC) in hyperbolic 3-space H3. We give a new, geometrically transparent proof of the existence of a CMC surface spanning any given Jordan curve on the sphere at infinity of H3, for mean curvature lying in the range (-1,1). Our proof does not require methods from geometric measure theory, and yields an immersed disk as solution. We then study the dependence of the solution surface on the boundary data. We view the set of H-surfaces (CMC surfaces with mean curvature equal to H) as consisting of the conformal H-harmonic maps. We therefore begin by showing smooth dependence on boundary data for H-harmonic maps (with |H| < 1) which solve a Dirichlet problem at infinity. This is achieved by showing that the linearised H-harmonic map operator is invertible as a map between appropriate function spaces. Finally we show smooth dependence on boundary data for H-surfaces which lie in a neighbourhood of the totally umbilic spherical caps {H}. This is achieved by studying the mapping properties of the so-called conformality operator. We use methods from complex geometry to show that the linearisation of this operator at a cap H is an isomorphism for all H ∈ (−1, 1)

Complete noncompact CMC surfaces in hyperbolic 3-space

In this thesis we study the asymptotic Plateau problem for surfaces with constant mean curvature (CMC) in hyperbolic 3-space H3. We give a new, geometrically transparent proof of the existence of a CMC surface spanning any given Jordan curve on the sphere at infinity of H3, for mean curvature lying in the range (-1,1). Our proof does not require methods from geometric measure theory, and yields an immersed disk as solution. We then study the dependence of the solution surface on the boundary data. We view the set of H-surfaces (CMC surfaces with mean curvature equal to H) as consisting of the conformal H-harmonic maps. We therefore begin by showing smooth dependence on boundary data for H-harmonic maps (with |H| < 1) which solve a Dirichlet problem at infinity. This is achieved by showing that the linearised H-harmonic map operator is invertible as a map between appropriate function spaces. Finally we show smooth dependence on boundary data for H-surfaces which lie in a neighbourhood of the totally umbilic spherical caps {H}. This is achieved by studying the mapping properties of the so-called conformality operator. We use methods from complex geometry to show that the linearisation of this operator at a cap H is an isomorphism for all H ∈ (−1, 1).EThOS - Electronic Theses Online ServiceGBUnited Kingdo