Seminars and Colloquia by Series

The phase transition in the random d-process

Series
Combinatorics Seminar
Time
Friday, August 26, 2016 - 15:05 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Lutz Warnke – Georgia Tech
One of the most interesting features of Erdös-Rényi random graphs is the `percolation phase transition', where the global structure intuitively changes from only small components to a single giant component plus small ones. In this talk we discuss the percolation phase transition in the random d-process, which corresponds to a natural algorithmic model for generating random regular graphs (starting with an empty graph on n vertices, it evolves by sequentially adding new random edges so that the maximum degree remains at most d). Our results on the phase transition solve a problem of Wormald from 1997, and verify a conjecture of Balinska and Quintas from 1990. Based on joint work with Nick Wormald (Monash University).

Lifting Homeomorphisms of Cyclic Branched Covers of Spheres

Series
Geometry Topology Seminar
Time
Monday, August 22, 2016 - 14:05 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Rebecca Winarski – University of Wisconsin at Milwaukee
Birman and Hilden ask: given finite branched cover X over the 2-sphere, does every homeomorphism of the sphere lift to a homeomorphism of X? For covers of degree 2, the answer is yes, but the answer is sometimes yes and sometimes no for higher degree covers. In joint work with Ghaswala, we completely answer the question for cyclic branched covers. When the answer is yes, there is an embedding of the mapping class group of the sphere into a finite quotient of the mapping class group of X. In a family where the answer is no, we find a presentation for the group of isotopy classes of homeomorphisms of the sphere that do lift, which is a finite index subgroup of the mapping class group of the sphere. Our family introduces new examples of orbifold Picard groups of subloci of Teichmuller space that are finitely generated but not cyclic.

GT MAP Workshop on Materials

Series
GT-MAP Seminar
Time
Wednesday, August 17, 2016 - 09:30 for 8 hours (full day)
Location
Skiles 249
Speaker
Various speakers – Georgia Tech
The workshop will launch the themetic semester on Material for GT-MAP activities. This is a three day workshop: The first two days (Wed, Thurs) focusing on the theme of Material, and third day includes broad research topics, open to introducing your research. See the complete Schedule.

Difference of convex functions for eigenvalue problems

Series
Applied and Computational Mathematics Seminar
Time
Monday, August 8, 2016 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Prof. Yunho Kim – UNIST, Korea
Inspired by the usefulness of difference of convex functions in some problems, e.g. sparse representations, we use such an idea of difference of convex functions to propose a method of finding an eigenfunction of a self-adjointoperator. In a matrix setting, this method always finds an eigenvector of a symmetric matrix corresponding to the smallest eigenvalue without solving Ax=b. In fact, such a matrix A is allowed to be singular, as well. We can apply the same setting to a generalized eigenvalue problem. We will discuss its convergence as well.

Final presentations for 2016 IMPACT REU

Series
Other Talks
Time
Wednesday, July 20, 2016 - 10:00 for 2 hours
Location
Skiles ground floor atrium
Speaker
IMPACT REU – Georgia Tech
Poster presentations by Ibrahim Apata (Morehouse), Chelsea Huston (Spelman), Jason Kolbush (Georgia Tech), Isabella Nang (Georgia State), Taylor Strickland (Agnes Scott), and Ida De Vierno (Georgia Tech).

What is the Shortest Distance between Two Points? Well, Maybe That's Not the Right Question.

Series
Other Talks
Time
Friday, July 15, 2016 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Kaye Husbands Fealing, Chair and Professor – School of Public Policy, Georgia Tech
At a recent leadership training workshop, where chairs, deans and provosts engaged in "Vegas Rules" discussions about how to develop talent in staff and ourselves, I was asked the question-What was the thing that I enjoyed most during my childhood? Of course I responded: Solving math problems fast! But how does that relate to my research on pricing strategies in the automotive industry, technological aspirations in the developing-country context, earnings and employment differentials by race/ethnicity and gender in various market sectors, and return on investment in food safety research? The answers to this question will be the focus of this talk. The key takeaways will be that pathways meander, enjoy scientific explorations, and the quickest pathway to the crown of one's career is not necessarily the most fulfilling.

Limits to estimating the severity of emerging epidemics due to inherent noise

Series
Mathematical Biology Seminar
Time
Wednesday, July 6, 2016 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Bradford Taylor – School of Biology, Georgia Tech

Please Note: When a disease outbreak occurs, mathematical models are used to estimate the potential severity of the epidemic. The average number of secondary infections resulting from the initial infection or reproduction number, R_0, quantifies this severity. R_0 is estimated from the models by leveraging observed case data and understanding of disease epidemiology. However, the leveraged data is not perfect. How confident should we be about measurements of R_0 given noisy data? I begin my talk by introducing techniques used to model epidemics. I show how to adapt standard models to specific diseases by using the 2014-2015 Ebola outbreak in West Africa as an example throughout the talk. Nest, I introduce the inverse problem: given real data tracking the infected population how does one estimate the severity of the outbreak. Through a novel method I show how to account for both inherent noise arising from discrete interactions between individuals (demographic stochasticity) and from uncertainty in epidemiological parameters. By applying this, I argue that the first estimates of R_0 during the Ebola outbreak were overconfident because demographic stochasticity was ignored. This talk will be accessible to undergraduates.

Algebraic models of gene regulatory networks

Series
Mathematical Biology Seminar
Time
Wednesday, June 29, 2016 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Elena Dimitrova – Clemson University
Progress in systems biology relies on the use of mathematical and statistical models for system level studies of biological processes. This talk will focus on discrete models of gene regulatory networks and the challenges they present, in particular data selection and model stability. Careful data selection is important for model identification since the process is sensitive to the amount and type of data used as input. We will discuss a criterion for deciding when a set of data points identifies an algebraic model with special minimality properties. Stability is another important requirement for models of gene regulatory networks. Canalizing functions, a particular class of Boolean functions, show stable dynamic behavior and are thus suitable for expressing gene regulatory relationships. However, in practice, relaxing the canalizing requirement on some variables is appropriate. We will present the class of partially nested canalizing functions and some of their properties and applications.

An Algebraic Introduction to Multiview Geometry and Tensors

Series
Algebra Seminar
Time
Monday, June 27, 2016 - 11:05 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Luke Oeding – Auburn University
In Multiview Geometry, a field of Computer Vision one is interested in reconstructing 3-dimensional scenes from 2-dimensional images. I will review the basic concepts in this area from an algebraic viewpoint, in particular I'll discuss epipolar geometry, fundamental matrices, and trifocal and quadrifocal tensors. I'll also highlight some in open problems about the algebraic geometry that arise.This will be an introductory talk, and only a background in basic linear algebra should be necessary to follow.

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