Seminars and Colloquia by Series

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 EllnerCornell
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 LokshtanovInstitutt 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 PanGeorgia 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 CrootSchool 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 GaribaldiEmory 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 ShinMassachusetts 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 CaseyGeorgia 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 XinSchool 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.

Global Uniform Risk Bounds for Wavelet Deconvolution Estimators

Series
Job Candidate Talk
Time
Thursday, February 4, 2010 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 269
Speaker
Karim LouniciUniversity of Cambridge
We consider the statistical deconvolution problem where one observes $n$ replications from the model $Y=X+\epsilon$, where $X$ is the unobserved random signal of interest and where $\epsilon$ is an independent random error with distribution $\varphi$. Under weak assumptions on the decay of the Fourier transform of $\varphi$ we derive upper bounds for the finite-sample sup-norm risk of wavelet deconvolution density estimators $f_n$ for the density $f$ of $X$, where $f: \mathbb R \to \mathbb R$ is assumed to be bounded. We then derive lower bounds for the minimax sup-norm risk over Besov balls in this estimation problem and show that wavelet deconvolution density estimators attain these bounds. We further show that linear estimators adapt to the unknown smoothness of $f$ if the Fourier transform of $\varphi$ decays exponentially, and that a corresponding result holds true for the hard thresholding wavelet estimator if $\varphi$ decays polynomially. We also analyze the case where $f$ is a 'supersmooth'/analytic density. We finally show how our results and recent techniques from Rademacher processes can be applied to construct global nonasymptotic confidence bands for the density $f$.

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