Abstracts for the Seminar
 Discrete Geometry and Combinatorics
 Fall 2016

Speaker:  Victor Alexandrov, Sobolev Institute of Mathematics, Novosibirsk
Title: Continuous deformations of polyhedra that do not alter the dihedral angles
Time: 2:30 PM, Monday, September 19, 2016
Place:  Malott 206

Abstract: We prove that, both in Lobachevskij and spherical 3-spaces, there exist nonconvex compact boundary-free polyhedral surfaces without selfintersections which admit nontrivial continuous deformations preserving all dihedral angles and study properties of such polyhedral surfaces. In particular, we prove that (1) the volume of the domain, bounded by such a polyhedral surface, is necessarily constant during such a deformation; (2) for some families of polyhedral surfaces, the surface area, the total mean curvature, and the Gauss curvature of some vertices are nonconstant during deformations that preserve the dihedral angles; (3) in the both spaces, there exist tilings that possess nontrivial deformations preserving the dihedral angles of every tile in the course of deformation.

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