Away talks, the week of October 18, 2010

A busy week. On Monday, Louis Theran is speaking at the University of Maryland Geometry and Topology Seminar.

Title: Generic rigidity of periodic frameworks

Abstract: A planar periodic bar-joint framework is an infinite structure, periodic with respect to a lattice, made of fixed-length bars connected by universal joints with full rotational freedom. The allowed continuous motions are those that preserve the length and connectivity of the bars. Furthermore, the lattice is allowed to deform.


On Tuesday, Chris Atkinson is speaking at the CUNY Graduate Center Geometry and Topology Seminar.

Title: Two-sided combinatorial volume bounds for non-obtuse hyperbolic polyhedra.

Abstract: We give a method for computing upper and lower bounds for
the volume of a non–obtuse hyperbolic polyhedron in terms of the
combinatorics of the 1-skeleton.  We will first describe how to obtain
volume bounds in the right-angled case and then show how the more
general case follows from techniques related to the proof  of
Thurston’s Orbifold Theorem and Schlaefli’s formula.

On Thursday, David Futer is Speaking at the Brigham Young University Geometry Seminar

Title: Surface quotients of hyperbolic buildings

Abstract: Bourdon’s building is a negatively curved 2-complex built out of hyperbolic right-angled polygons. Its automorphism group is large (uncountable) and remarkably rich. We study, and mostly answer, the question of when there is a discrete subgroup of the automorphism group such that the quotient is a closed surface of genus g. The cases that we treat involve a fun melange of combinatorics, homology theory, and group theory. The cases that are still open quickly lead to open questions in number theory. This is joint work with Anne Thomas.

On Friday,  Igor Rivin is speaking at the Institute for Advanced Study Geometry and Cell Complexes Seminar:

Title: Spectral Geometry of Random Graphs

Abstract: we will describe various models of sparse and planar graphs and the associated distributions of eigenvalues (and eigenvalue spacings) which come up. The talk will be light on theorems, and heavy on experimental data.

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