316 research outputs found
Holomorphic vector fields and quadratic differentials on planar triangular meshes
Given a triangulated region in the complex plane, a discrete vector field
assigns a vector to every vertex. We call such a vector
field holomorphic if it defines an infinitesimal deformation of the
triangulation that preserves length cross ratios. We show that each holomorphic
vector field can be constructed based on a discrete harmonic function in the
sense of the cotan Laplacian. Moreover, to each holomorphic vector field we
associate in a M\"obius invariant fashion a certain holomorphic quadratic
differential. Here a quadratic differential is defined as an object that
assigns a purely imaginary number to each interior edge. Then we derive a
Weierstrass representation formula, which shows how a holomorphic quadratic
differential can be used to construct a discrete minimal surface with
prescribed Gau{\ss} map and prescribed Hopf differential.Comment: 17 pages; final version, to appear in "Advances in Discrete
Differential Geometry", ed. A. I. Bobenko, Springer, 2016; references adde
Thurston's sphere packings on 3-dimensional manifolds, I
Thurston's sphere packing on a 3-dimensional manifold is a generalization of
Thusrton's circle packing on a surface, the rigidity of which has been open for
many years. In this paper, we prove that Thurston's Euclidean sphere packing is
locally determined by combinatorial scalar curvature up to scaling, which
generalizes Cooper-Rivin-Glickenstein's local rigidity for tangential sphere
packing on 3-dimensional manifolds. We also prove the infinitesimal rigidity
that Thurston's Euclidean sphere packing can not be deformed (except by
scaling) while keeping the combinatorial Ricci curvature fixed.Comment: Arguments are simplife
The modular geometry of Random Regge Triangulations
We show that the introduction of triangulations with variable connectivity
and fluctuating egde-lengths (Random Regge Triangulations) allows for a
relatively simple and direct analyisis of the modular properties of 2
dimensional simplicial quantum gravity. In particular, we discuss in detail an
explicit bijection between the space of possible random Regge triangulations
(of given genus g and with N vertices) and a suitable decorated version of the
(compactified) moduli space of genus g Riemann surfaces with N punctures. Such
an analysis allows us to associate a Weil-Petersson metric with the set of
random Regge triangulations and prove that the corresponding volume provides
the dynamical triangulation partition function for pure gravity.Comment: 36 pages corrected typos, enhanced introductio
Triangulated Riemann surfaces with boundary and the Weil-Petersson Poisson structure
Given a Riemann surface with boundary S, the lengths of a maximal system of
disjoint simple geodesic arcs on S that start and end at the boundary of S
perpendicularly are coordinates on the Teichmueller space T(S). We compute the
Weil-Petersson Poisson structure on T(S) in this system of coordinates and we
prove that it limits pointwise to the piecewise-linear Poisson structure
defined by Kontsevich on the arc complex of S. As a byproduct of the proof, we
obtain a formula for the first-order variation of the distance between two
closed geodesics under Fenchel-Nielsen deformation.Comment: 44 pages, 12 figures (LaTeX 2e). Published versio
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