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Research Seminars: Geometry and Topology


Past Geometry and Topology:

Fall 2018

Time & Location: All talks are on Thursday in Gibson Hall 400D at 12:30 PM unless otherwise noted.
Organizer: Slawomir Kwasik


October 18

Topic: On the reconstruction problem for geodesic subspaces in the Euclidean Space

Rafał Komendarczyk - Tulane University

Abstract:

We develop a persistence based algorithm for the homology/homotopy groups reconstruction of the unknown underlying geodesic subspace of R^n from a point cloud. In the case of a metric graph, we can output a subspace which is an arbitrarily good approximation of the underlying graph. This is a collaborative work in progress.


October 25

Finite-type knot invariants and a proof of the Goussarov Theorem


Robyn Brooks - Tulane University

Abstract



Finite-type knot invariants represent an active research area in knot theory.  The Goussarov Theorem shows that all such invariants can be read from the Gauss diagram of a knot.  In this talk, I will give a proof of this theorem, which provides a method by which one can generate a formula to determine the value of an invariant from its Gauss diagram.

November 1

Discrete Morse theory and its applications to metric graph reconstruction


Sushovan Majhi - Tulane University

Abstract:

Discrete Morse theory has recently been used as a powerful tool for topological reconstruction and simplification in the field of Applied and Computational Topology.  We discuss some its very recent and successful applications in data analysis. In particular, we talk about a recent development in threshold-based topological and geometric reconstruction of metric graphs from a density concentrated around it.


November 15

Density bounds on binary packings of disks in the plane


Ali Mohajer - Tulane University

Abstract:


In this talk we develop methods for establishing upper density bounds for saturated two-radius packings of disks in the plane.

Define the homogeneity of a packing of disks in the plane to be the infimum of the ratio of radii of disks in the packing. It has been known since 1953 (L. Fejes-Toth) that if the homogeneity of a packing is close enough to 1, the density of that packing cannot exceed $\frac{$\pi}{\sqrt{12}},$ the upper bound on the density of a single-radius packing. "Close enough” was refined in 1963 by August Florian to mean a homogeneity in the interval (0.902…, 1], and in 1969, Gerd Blind extended the left bound of this interval to approximately 0.742.

In 2003, sharp upper density bounds were established by Aladar Heppes for a handful of two-radius packings at homogeneities which admit arrangements wherein each disk is tangent to a ring of disks, each of which is tangent to its two cyclic neighbors. We will discuss recent progress in establishing a bound sharper than the best one known for binary packings at a homogeneity that does not admit such regularity.


Date

Topic


Speaker - Institution

Abstract: TBA


Date

Topic


Speaker - Institution

Abstract: TBA


Mathematics Department, 424 Gibson Hall, New Orleans, LA 70118 504-865-5727 math@math.tulane.edu