Seminars and Colloquia by Series

Introduction to Sheaf Theory

Series
Other Talks
Time
Wednesday, September 9, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 269
Speaker
John Etnyre – Ga Tech
In these talks we will introduced the basic definitions and examples of presheaves, sheaves and sheaf spaces. We will also explore various constructions and properties of these objects.

Grain boundary motion in thin films

Series
Applied and Computational Mathematics Seminar
Time
Wednesday, September 9, 2009 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 114
Speaker
Amy Novick-Cohen – Technion
Grain boundaries within polycrystalline materials are known to be governed by motion by mean curvature. However, when the polycrystalline specimen is thin, such as in thin films, then the effects of the exterior surfaces start to play an important role. We consider two particularly simple geometries, an axi-symmetric geometry, and a half loop geometry which is often employed in making measurements of the kinetic coefficient in the motion by mean curvature equation, obtaining corrective terms which arise due to the coupling of grain boundaries to the exterior surface.   Joint work with Anna Rotman, Arkady Vilenkin & Olga Zelekman-Smirin

Some Problems and Results in Additive Combinatorics.

Series
Research Horizons Seminar
Time
Wednesday, September 9, 2009 - 12:00 for 1 hour (actually 50 minutes)
Location
Skiles 171
Speaker
Ernie Croot – School of Mathematics, Georgia Tech –
Additive combinatorics is a relatively new field, with many diverse and exciting research programmes. In this talk I will discuss two of these programmes -- the continuing development of sum-product inequalities, and the unfolding progress on arithmetic progressions -- along with some new results proved by me and my collaborators. Hopefully I will have time to mention some nice research problems as well.

A polyhedral study of the mixed integer cut

Series
ACO Student Seminar
Time
Wednesday, September 9, 2009 - 12:00 for 1 hour (actually 50 minutes)
Location
ISyE Executive Classroom
Speaker
Steve Tyber – ISyE, Georgia Tech
In 1969, Gomory introduced the master group polyhedron for pure integer programs and derives the mixed integer cut (MIC) as a facet of a special family of these polyhedra. We study the MIC in this framework, characterizing both its facets and extreme points; next, we extend our results under mappings between group polyhedra; and finally, we conclude with related open problems. No prior knowledge of algebra or the group relaxation is assumed. Terminology will be introduced as needed. Joint work with Ellis Johnson.

On asymptotics, structure and stability for multicomponent reactive flows

Series
PDE Seminar
Time
Tuesday, September 8, 2009 - 15:05 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Konstantina Trivisa – University of Maryland, College Park
Multicomponent reactive flows arise in many practical applicationssuch as combustion, atmospheric modelling, astrophysics, chemicalreactions, mathematical biology etc. The objective of this work isto develop a rigorous mathematical theory based on the principles ofcontinuum mechanics. Results on existence, stability, asymptotics as wellas singular limits will be discussed.

Deterministic Algorithm for Lovasz Local Lemma

Series
Combinatorics Seminar
Time
Friday, September 4, 2009 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Karthekeyan Chandrasekaran – College of Computing
Lovasz Local Lemma (LLL) is a powerful result in probability theory that states that the probability that none of a set of bad events happens is nonzero if the probability of each event is small compared to the number of events that depend on it. It is often used in combination with the probabilistic method for non-constructive existence proofs. A prominent application of LLL is to k-CNF formulas, where LLL implies that, if every clause in the formula shares variables with at most d \le 2^k/e other clauses then such a formula has a satisfying assignment. Recently, a randomized algorithm to efficiently construct a satisfying assignment was given by Moser. Subsequently Moser and Tardos gave a randomized algorithm to construct the structures guaranteed by the LLL in a very general algorithmic framework. We will address the main problem left open by Moser and Tardos of derandomizing their algorithm efficiently when the number of other events that any bad event depends on is possibly unbounded. An interesting special case of the open problem is the k-CNF problem when k = \omega(1), that is, when k is more than a constant.

The McKean--Vlasov Equation in Finite Volume

Series
Math Physics Seminar
Time
Thursday, September 3, 2009 - 16:00 for 1 hour (actually 50 minutes)
Location
Skiles 269
Speaker
Lincoln Chayes – UCLA –
The McK--V system is a non--linear diffusion equation with a non--local non--linearity provided by convolution. Recently popular in a variety of applications, it enjoys an ancient heritage as a basis for understanding equilibrium and near equilibrium fluids. The model is discussed in finite volume where, on the basis of the physical considerations, the correct scaling (for the model itself) is identified. For dimension two and above and in large volume, the phase structure of the model is completely elucidated in (somewhat disturbing) contrast to dynamical results. This seminar represents joint work with V. Panferov.

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