Seminars and Colloquia by Series

Series: Other Talks
Friday, August 20, 2010 - 14:00 , Location: Klaus 1447 , Kamal Jain , Microsoft Research, Redmond, WA , Organizer:

This talk should be non-technical except the last few slides. The talk is
based on a work done in collaboration with Denis Charles, Max Chickering,
Nikhil Devanur, and Manan Sanghi, all from Microsoft.

Lopsided bipartite graphs naturally appear in advertising setting. One side is all the eyeballs and the other side is all the advertisers. An edge is when an advertiser wants to reach an eyeball, aka, ad targeting. Such a bipartite graph is lopsided because there are only a small number of advertisers but a large number of eyeballs. We give algorithms which have running time proportional to the size of the smaller side, i.e., the number of advertisers. One of the main ideas behind our algorithm and as well as the analysis is a property, which we call, monotonic quality bounds. Our algorithm is flexible as it could easily be adapted for different kinds of objective functions. Towards the end of the talk we will describe a new matching polytope. We show that our matching polytope is not only a new linear program describing the classical matching polytope, but is a new polytope together with a new linear program. This part of the talk is still theoretical as we only know how to solve the new linear program via an ellipsoid algorithm. One feature of the polytope, besides being intriguing, is that it has some notion of fairness built in. This is important for advertising since if an advertiser wants to reach 10 million users of type A or type B, advertiser won't necessarily be happy if we show the ad to 10 million users of type A only (though it fulfills the advertising contract in a technical sense).
Series: Other Talks
Saturday, June 26, 2010 - 11:00 , Location: Skiles 169 , Various speakers , Georgia Tech , Organizer: Ernie Croot
This mini-conference will feature about six speakers on various topics in additive combinatorics. 
Series: Other Talks
Saturday, May 15, 2010 - 08:00 , Location: Emory University , East Coast Computer Algebra Day 2010 , Department of Mathematics and Computer Science, Emory University , Organizer:

Anton Leykin is an invited speaker presenting "Certified numerical solving of systems of polynomial equations"

East Coast Computer Algebra Day (ECCAD) is an informal one-day meeting for those active or interested in computer algebra. It provides opportunities to learn and to share new results and work in progress.  The schedule includes invited speakers, a panel discussion, and contributed posters and software demonstrations. Importantly, plenty of time is allowed for unstructured interaction among the participants.  Researchers, teachers, students, and users of computer algebra are all welcome! Visit ECCAD for more details.
Series: Other Talks
Thursday, April 29, 2010 - 19:00 , Location: Skiles 202 , Michael Lacey , Georgia Tech , Organizer:
Club Math Presents The Mathematics of Futurama, by Dr. Michael Lacey. 
Series: Other Talks
Tuesday, April 13, 2010 - 17:15 , Location: Skiles 269 , Antoine Chambert-Loir , Universite de Rennes/Institute for Advanced Study , Organizer: Matt Baker
Series: Other Talks
Tuesday, April 13, 2010 - 16:00 , Location: Skiles 269 , Venapally Suresh , University of Hyderabad / Emory University , Organizer: Matt Baker
Let k be a global field or a local field. Class field theory says that every central division algebra over k is cyclic. Let l be a prime not equal to the characteristic of k. If k contains a primitive l-th root of unity, then this leads to the fact that every element in H^2(k, µ_l ) is a symbol. A natural question is a higher dimensional analogue of this result: Let F be a function field in one variable over k which contains a primitive l-th root of unity. Is every element in H^3(F, µ_l ) a symbol? In this talk we answer this question in affirmative for k a p-adic field or a global field of positive characteristic. The main tool is a certain local global principle for elements of H^3(F, µ_l ) in terms of symbols in H^2(F µ_l ). We also show that this local-global principle is equivalent to the vanishing of certain unramified cohomology groups of 3-folds over finite fields.
Series: Other Talks
Monday, April 12, 2010 - 17:00 , Location: Klaus 1116W , Richard Schoen , Stanford University , Organizer: John McCuan
In 1854 Riemann extended Gauss' ideas on curved geometries from two dimensional surfaces to higher dimensions. Since that time mathematicians have tried to understand the structure of geometric spaces based on their curvature properties. It turns out that basic questions remain unanswered in this direction. In this lecture we will give a history of such questions for spaces with positive curvature, and describe the progress that has been made as well as some outstanding conjectures which remain to be settled.
Series: Other Talks
Monday, April 12, 2010 - 08:00 , Location: Skiles 269 , Southeast Geometry Seminar , School of Mathematics, Georgia Tech , Organizer: John McCuan
The Southeast Geometry Seminar is a series of semiannual one-day events focusing on geometric analysis. These events are hosted in rotation by the following institutions: The University of Alabama at Birmingham; The Georgia Institute of Technology; Emory University; The University of Tennessee Knoxville. The presentations will include topics on geometric analysis, and related fields, such as partial differential equations, general relativity, and geometric topology. See the Schedule for times and abstracts of talks.
Series: Other Talks
Wednesday, April 7, 2010 - 16:30 , Location: Skiles 255 , Allan Sly , Microsoft Research, Redmond, WA , Organizer: Prasad Tetali
Intensive study throughout the last three decades has yielded a rigorous understanding of the spectral-gap of the Glauber dynamics for the Ising model on $Z^2$ everywhere except at criticality. While the critical behavior of the Ising model has long been the focus for physicists, mathematicians have only recently developed an understanding of its critical geometry with the advent of SLE, CLE and new tools to study conformally invariant systems.  A rich interplay exists between the static and dynamic models. At the static phase-transition for Ising, the dynamics is conjectured to undergo a critical slowdown: At high temperature the inverse-gap is $O(1)$, at the critical $\beta_c$ it is polynomial in the side-length and at low temperature it is exponential in it. A long series of papers verified this on $Z^2$ except at $\beta=\beta_c$ where the behavior remained unknown.  In this work we establish the first rigorous polynomial upper bound for the critical mixing, thus confirming the critical slowdown for the Ising model in $Z^2$. Namely, we show that on a finite box with arbitrary (e.g. fixed, free, periodic) boundary conditions, the inverse-gap at $\beta=\beta_c$ is polynomial in the side-length. The proof harnesses recent understanding of the scaling limit of critical Fortuin-Kasteleyn representation of the Ising model together with classical tools from the analysis of Markov chains.  Based on joint work with Eyal Lubetzky.
Series: Other Talks
Tuesday, April 6, 2010 - 11:00 , Location: ISyE Executive Classroom , Adrian Lewis , School of Operations Research and Information, Cornell University , Organizer: Annette Rohrs
Concrete optimization problems, while often nonsmooth, are not pathologically so. The class of "semi-algebraic" sets and functions - those arising from polynomial inequalities - nicely exemplifies nonsmoothness in practice. Semi-algebraic sets (and their generalizations) are common, easy to recognize, and richly structured, supporting powerful variational properties. In particular I will discuss a generic property of such sets - partial smoothness - and its relationship with a proximal algorithm for nonsmooth composite minimization, a versatile model for practical optimization.

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