Seminars and Colloquia by Series

On the Chvatal Closure of a Strictly Convex Body

Series
ACO Student Seminar
Time
Wednesday, February 10, 2010 - 13:30 for 1 hour (actually 50 minutes)
Location
ISyE Executive Classroom
Speaker
Daniel Dadush – ISyE ACO, Georgia Tech
The analysis of Chvatal Gomory (CG) cuts and their associated closure for polyhedra was initiated long ago in the study of integer programming. The classical results of Chvatal (73) and Schrijver (80) show that the Chvatal closure of a rational polyhedron is again itself a rational polyhedron. In this work, we show that for the class of strictly convex bodies the above result still holds, i.e. that the Chvatal closure of a strictly convex body is a rational polytope.This is joint work with Santanu Dey (ISyE) and Juan Pablo Vielma (IBM).

Modeling coral disease: within-host dynamics, individual demography, and population consequences

Series
Mathematical Biology Seminar
Time
Wednesday, February 10, 2010 - 11:00 for 1 hour (actually 50 minutes)
Location
255 Skiles
Speaker
Steven Ellner – Cornell –
Emerging diseases have played an important role in the major recent declinesof coral reef cover worldwide. I will present some theoretical efforts aimedat understanding processes of coral disease development and itsconsequences: (1) how the development of coral disease is regulated bymicrobial population interactions within the mucus layer surrounding thecoral, and (2) the effects of a recent fungal epizootic on populations of aCaribbean sea fan coral, focusing on how this species was able to recover tohigh abundance and low disease prevalence. Collaborators on this workinclude John Bruno (UNC-CH); C. Drew Harvell, Laura Jones, and JustinMao-Jones (Cornell), and Kim Ritchie (MOTE Marine Lab).

ARC Colloquium - Saving Space by Algebraization

Series
Other Talks
Time
Wednesday, February 10, 2010 - 10:03 for 1 hour (actually 50 minutes)
Location
Klaus 1116W
Speaker
Daniel Lokshtanov – Institutt for Informatikk, Universitetet i Bergen
The Subset Sum and Knapsack problems are fundamental NP-complete problems and the pseudo-polynomial time dynamic programming algorithms for them appear in every algorithms textbook. The algorithms require pseudo-polynomial time and space. Since we do not expect polynomial time algorithms for Subset Sum and Knapsack to exist, a very natural question is whether they can be solved in pseudo-polynomial time and polynomial space. In this paper we answer this question affrmatively, and give the first pseudo-polynomial time, polynomial space algorithms for these problems. Our approach is based on algebraic methods and turns out to be useful for several other problems as well. If there is time i will also show how our method can be applied to give polynomial space exact algorithms for the classical Traveling Salesman, Weighted Set Cover and Weighted Steiner Tree problems. Joint work with Jesper Nederlof.

L^1 convergence toward Barenblatt solution of isentropic porous medium flows

Series
PDE Seminar
Time
Tuesday, February 9, 2010 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Ronghua Pan – Georgia Tech –
Darcy's law was observed in the motion of porous medium flows. This talk aims at the mathematical justification on Darcy's law as long time limit from compressible Euler equations with damping. In particularly, we shall showthat any physical solution with finite total mass shall converges in L^1 distance toward the Barenblatt's solution of the same mass for the Porous Medium Equation. The approach will explore the dissipation of the entropy inequality motivated by the second law of thermodynamics. This is a joint work with Feimin Huang and Zhen Wang.

A Probabilistic Technique for Finding Almost Periods in Additive Combinatorics

Series
Research Horizons Seminar
Time
Tuesday, February 9, 2010 - 12:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Ernie Croot – School of Math, Georgia Tech

Please Note: Hosted by: Huy Huynh and Yao Li

Olof Sisask and myself have produced a new probabilistic technique for finding `almost periods' of convolutions of subsets of finite groups. In this talk I will explain how this has allowed us to give (just recently) new bounds on the length of the longest arithmetic progression in a sumset A+A.

There is no "Theory of Everything" inside E8

Series
Algebra Seminar
Time
Monday, February 8, 2010 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 171
Speaker
Skip Garibaldi – Emory University
The "Exceptionally Simple Theory of Everything" has been the subject of articles in The New Yorker (7/21/08), Le Monde (11/20/07), the Financial Times (4/25/09), The Telegraph (11/10/09), an invited talk at TED (2/08), etc. Despite positive descriptions of the theory in the popular press, it doesn't work. I'll explain a little of the theory, the mathematical reasons why it doesn't work, and a theorem (joint work with Jacques Distler) that says that no similar theory can work. This talk should be accessible to all graduate students in mathematics.

Message Passing Networks

Series
Other Talks
Time
Friday, February 5, 2010 - 15:00 for 1 hour (actually 50 minutes)
Location
Klaus 1116E
Speaker
Jinwoo Shin – Massachusetts Institute of Technology

Please Note: Refreshments in Room 2222, Klaus Building from 2-3 PM.

Simple, distributed and iterative algorithms, popularly known as the message passing algorithms, have emerged as the architecture of choice for engineered networks as well as cannonical behavioral model for societal and biological networks. Despite their simplicity, message passing algorithms have been surprisingly effective. In this talk, I will try to argue in favor of such algorithms by means of two results in the context of designing efficient medium access in wireless networks and modeling agent behavior in road transportation networks. See the full abstract,

Intro to Branched Covers

Series
Geometry Topology Working Seminar
Time
Friday, February 5, 2010 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 269
Speaker
Meredith Casey – Georgia Tech
Exact Topic TBA. Talk will be a general survery of branched covers, possibly including covers from the algebraic geometry perspective. In addition we will look at branched coveres in higher dimensions, in the contact world, and my current research interests. This talk will be a general survery, so very little background is assumed.

The existence and uniqueness of one minimization problem

Series
SIAM Student Seminar
Time
Friday, February 5, 2010 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 255
Speaker
Linwei Xin – School of Mathematics, Georgia Tech
We are dealing with the following minimization problem: inf {I(\mu): \mu is a probability measure on R and \int f(x)=t_{0}}, where I(\mu) = \int (x^2)/2 \mu(dx) + \int\int log|x-y|^{-1} \mu(dx)\mu(dy), f(x) is a bounded continuous function and t is a given real number. Its motivation and its connection to radom matrices theory will be introduced. We will show that the solution is unique and has a compact support. The possible extension of the class of f(x) will be discussed.

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