Seminars and Colloquia by Series

Surjective homomorphism between surface braid groups

Series
Geometry Topology Seminar
Time
Tuesday, June 27, 2017 - 14:05 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Lei Chen – University of Chicago
I will talk about homomorphisms between surface braid groups. Firstly, we will see that any surjective homomorphism from PB_n(S) to PB_m(S) factors through a forgetful map. Secondly, we will compute the automorphism group of PB_n(S). It turns out to be the mapping class group when n>1.

Experimental statistics of veering triangulations.

Series
Geometry Topology Seminar
Time
Friday, June 23, 2017 - 10:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
William Worden – Temple University –
Certain fibered hyperbolic 3-manifolds admit a layered veering triangulation, which can be constructed algorithmically given the stable lamination of the monodromy. These triangulations were introduced by Agol in 2011, and have been further studied by several others in the years since. We present experimental results which shed light on the combinatorial structure of veering triangulations, and its relation to certain topological invariants of the underlying manifold. We will begin by discussing essential background material, including hyperbolic manifolds and ideal triangulations, and more particularly fibered hyperbolic manifolds and the construction of the veering triangulation.

Self-similar tilings of General Fractal Blow-ups and Anderson Putnam Theory

Series
Analysis Seminar
Time
Wednesday, June 21, 2017 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Michael F. Barnsley – Australian National University
In this seminar I will discuss current work, joint with AndrewVince and Alex Grant. The goal is to tie together several related areas, namelytiling theory, IFS theory, and NCG, in terms most familiar to fractal geometers.Our focus is on the underlying code space structure. Ideas and a conjecture willbe illustrated using the Golden b tilings of Robert Ammann

Normal closures of mapping classes

Series
Geometry Topology Seminar
Time
Tuesday, June 20, 2017 - 14:05 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Dan Margalit and Justin Lanier – Georgia Tech
We give a simple geometric criterion for an element to normally generate the mapping class group of a surface. As an application of this criterion, we show that when a surface has genus at least 3, every periodic mapping class except for the hyperelliptic involution normally generates. We also give examples of pseudo-Anosov elements that normally generate when genus is at least 2, answering a question of D. Long.

Parallel Connections of Bilinear Systems

Series
Other Talks
Time
Thursday, May 25, 2017 - 11:00 for 1 hour (actually 50 minutes)
Location
TSRB 132
Speaker
Guenther Dirr – University of Wuzburg
First, we present a necessary and sufficient conditions for accessibility of bilinear systems evolving on semisimple (matrix) Lie groups. From this, we derive a controllability criterion for parallel connections of bilinear systems which gets a if-and-only-if condition in the case of compact Lie groups. Finally, we present a key application from quantum control.

Elusive problems in extremal graph theory

Series
Graph Theory Seminar
Time
Thursday, May 18, 2017 - 15:05 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Daniel Kral – University of Warwick
We study the uniqueness of optimal configurations in extremal combinatorics. An empirical experience suggests that optimal solutions to extremal graph theory problems can be made asymptotically unique by introducing additional constraints. Lovasz conjectured that this phenomenon is true in general: every finite feasible set of subgraph density constraints can be extended further by a finite set of density constraints such that the resulting set is satisfied by an asymptotically unique graph. We will present a counterexample to this conjecture and discuss related results. The talk is based on joint work with Andrzej Grzesik and Laszlo Miklos Lovasz.

Results on the construction of whiskered invariant tori for fibered holomorphic dynamics and on compensated domains.

Series
Dissertation Defense
Time
Monday, May 15, 2017 - 10:05 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Mikel Viana – Georgia Tech
We first discuss the construction of whiskered invariant tori for fibered holomorphic dynamics using a Nash-Moser iteration. The results are in a-posteriori form. The iterative procedure we present has numerical applications (it lends itself to efficient numerical implementations) since it is not based on transformation theory but rather in applying corrections which ameliorate notably the curse of dimensionality. Then we will discuss results on compensated domains in a Banach space.

A fractalization process for affine skew-products on the complex plane

Series
CDSNS Colloquium
Time
Wednesday, May 10, 2017 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Marc Jorba-Cusco – Universitat de Barcelona
Consider an affine skew product of the complex plane. \begin{equation}\begin{cases} \omega \mapsto \theta+\omega,\\ z \mapsto =a(\theta \mu)z+c, \end{cases}\end{equation}where $\theta \in \mathbb{T}$, $z\in \mathbb{C}$, $\omega$ is Diophantine, and $\mu$ and $c$ are real parameters. In this talk we show that, under suitable conditions, the affine skew product has an invariant curve that undergoes a fractalization process when $\mu$ goes to a critical value. The main hypothesis needed is the lack of reducibility of the system. A characterization of reducibility of linear skew-products on the complex plane is provided. We also include a linear and topological classification of these systems. Join work with: N\'uria Fagella, \`Angel Jorba and Joan Carles Tatjer

Working Group for Problems in Transport and Related Topics in Graphs

Series
GT-MAP Seminar
Time
Tuesday, May 9, 2017 - 10:00 for 8 hours (full day)
Location
Skiles 006
Speaker
Speaker list and schedule can be found at http://www.math.gatech.edu/hg/item/589661 – Organizers: Shui-Nee Chow, Wilfrid Gangbo, Prasad Tetali, and Haomin Zhou

Please Note: This workshop is sponsored by College of Science, School of Mathematics, GT-MAP and NSF.

The goal of this workshop is to bring together experts in various aspects of optimal transport and related topics on graphs (e.g., PDE/Numerics, Computational and Analytic/Probabilistic aspects).

Concordance and Dehn surgery

Series
Geometry Topology Seminar
Time
Monday, May 8, 2017 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Tye Lidman – NCSU
We will discuss a relation between some notions in three-dimensional topology and four-dimensional aspects of knot theory.

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