Seminars and Colloquia by Series

Probabilistic global well-posedness and Gibbs measure evolution for radial nonlinear Schr\"odinger and wave equations on the unit ball.

Series
CDSNS Colloquium
Time
Monday, February 24, 2014 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Aynur BulutUniv. of Michigan
In this talk we will discuss recent work, obtained in collaboration with Jean Bourgain, on new global well-posedness results along Gibbs measure evolutions for the radial nonlinear wave and Schr\"odinger equations posed on the unit ball in two and three dimensional Euclidean space, with Dirichlet boundary conditions. We consider initial data chosen according to a Gaussian random process associated to the Gibbs measures which arise from the Hamiltonian structure of the equations, and results are obtained almost surely with respect to these probability measures. In particular, this renders the initial value problem supercritical in the sense that there is no suitable local well-posedness theory for the corresponding deterministic problem, and our results therefore rely essentially on the probabilistic structure of the problem. Our analysis is based on the study of convergence properties of solutions. Essential ingredients include probabilistic a priori bounds, delicate estimates on fine frequency interactions, as well as the use of invariance properties of the Gibbs measure to extend the relevant bounds to arbitrarily long time intervals.

Georgia Scientific Computing Symposium 2014

Series
Other Talks
Time
Saturday, February 22, 2014 - 09:00 for 8 hours (full day)
Location
Kennesaw State University
Speaker
Georgia Scientific Computing SymposiumKennesaw State University

Please Note: Contact Yuliya Babenko, ybabenko@kennesaw.edu

The Georgia Scientific Computing Symposium 2014 will be held at Kennesaw State University (KSU) on Saturday, February 22. It is organized by KSU Departments of Mathematics and Statistics and Computer Science. There will be six plenary talks and a poster session. Graduate students, postdocs, and junior faculty are encouraged to present posters. For complete details and to register, see the symposium website

Optimizing Influenza Vaccine Allocation

Series
School of Mathematics Colloquium
Time
Thursday, February 20, 2014 - 11:00 for 1 hour (actually 50 minutes)
Location
Skyles 006
Speaker
Jan MedlockOregon State University
The emergence of the 2009 H1N1 influenza A strain and delays in production of vaccine against it illustrate the importance of optimizing vaccine allocation. We have developed computational optimization models to determine optimal vaccination strategies with regard to multiple objective functions: e.g.~deaths, years of life lost, economic costs. Looking at single objectives, we have found that vaccinating children, who transmit most, is robustly selected as the optimal allocation. I will discuss ongoing extensions to this work to incorporate multiple objectives and uncertainty.

Tales from the front, part I

Series
Professional Development Seminar
Time
Wednesday, February 19, 2014 - 16:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Christine HeitschGeorgia Tech
What does it take to find a faculty position? An overview of the application process, and group discussion of recent job searches. (Rescheduled from Feb 11th.)

Two Examples of Computational Math in Social Science and Engineering

Series
Research Horizons Seminar
Time
Wednesday, February 19, 2014 - 12:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Dr. ZhouSchool of Math
Abstract: In this talk, I will use two examples, the influence prediction in social media, and the short path in engineering, to illustrate how we use differential equations to establish models for problems in social science and engineering, and how to use mathematics to design efficient algorithms to compute the solutions. The talk is mainly for first or second year graduate students, and it is based on collaborative work with several faculty members and graduate students in SoM, ECE, CoC.

Obtaining Protein Energetics Using Adaptive Steered Molecular Dynamics

Series
Mathematical Biology Seminar
Time
Wednesday, February 19, 2014 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Rigoberto HernandezGT Chem & Biochem
The behavior and function of proteins necessarily occurs during nonequilibrium conditions such as when a protein unfolds or binds. The need to treat both the dynamics and the high-dimensionality of proteins and their environments presents significant challenges to theoretical or computational methods. The present work attempts to reign in this complexity by way of capturing the dominant energetic pathway in a particular protein motion. In particular, the energetics of an unfolding event can be formally obtained using steered molecular dynamics (SMD) and Jarzynski’s inequality but the cost of the calculation increases dramatically with the length of the pathway. An adaptive algorithm has been introduced that allows for this pathway to be nonlinear and staged while reducing the computational cost. The potential of mean force (PMF) obtained for neuropeptide Y (NPY) in water along an unfolding path confirmed that the monomeric form of NPY adopts the pancreatic-polypeptide (PP) fold. [J. Chem. Theory Comput. 6, 3026-3038 (2010); 10.1021/ct100320g.] Adaptive SMD can also be used to reconstruct the PMF obtained earlier for stretching decaalanine in vacuum at lower computational cost. [J. Chem. Phys. 136, 215104 (2012); 10.1063/1.4725183.] The PMF for stretching decaalanine in water solvent (using the TIP3P water potential) at 300K has now been obtained using adaptive SMD. [J. Chem. Theory Comput. 8, 4837 (2012); 10.1021/ct300709u] Not surprisingly, the stabilization from the water solvent reduces the overall work required to unfold it. However, the PMF remains structured suggesting that some regions of the energy landscape act partially as doorways. This is also further verified through a study of the hydrogen-bond breaking and formation along the stretching paths of decaalanine in vacuum and solvent. (Rescheduled from Feb 12th.)

Some New Comparison Results in Balls and Shells

Series
PDE Seminar
Time
Tuesday, February 18, 2014 - 15:05 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Jeffrey LangfordBucknell University
In a comparison theorem, one compares the solution of a given PDE to a solution of a second PDE where the data are "rearranged." In this talk, we begin by discussing some of the classical comparison results, starting with Talenti's Theorem. We then discuss Neumann comparison results, including a conjecture of Kawohl, and end with some new results in balls and shells involving cap symmetrization.

Tropical Laplacians and the Colin de Verdiere number of graphs

Series
Algebra Seminar
Time
Monday, February 17, 2014 - 15:05 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Eric KatzUniversity of Waterloo
Given a surface in space with a set of curves on it, one can ask whichpossible combinatorial arrangement of curves are possible. We give anenriched formulation of this question in terms of which two-dimensionalfans occur as the tropicalization of an algebraic surface in space. Ourmain result is that the arrangement is either degenerate or verycomplicated. Along the way, we introduce tropical Laplacians, ageneralization of graph Laplacians, explain their relation to the Colin deVerdiere invariant and to tensegrity frameworks in dynamics.This is joint work with June Huh.

Hamiltonian Circle Actions with Isolated Fixed Points on 6-Dimensional Symplectic Manifolds

Series
Geometry Topology Seminar
Time
Monday, February 17, 2014 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Andrew FanoeMorehouse College
The question of what conditions guarantee that a symplectic$S^1$ action is Hamiltonian has been studied for many years. Sue Tolmanand Jonathon Weitsman proved that if the action is semifree and has anon-empty set of isolated fixed points then the action is Hamiltonian.Furthermore, Cho, Hwang, and Suh proved in the 6-dimensional case that ifwe have $b_2^+=1$ at a reduced space at a regular level $\lambda$ of thecircle valued moment map, then the action is Hamiltonian. In this paper, wewill use this to prove that certain 6-dimensional symplectic actions whichare not semifree and have a non-empty set of isolated fixed points areHamiltonian. In this case, the reduced spaces are 4-dimensional symplecticorbifolds, and we will resolve the orbifold singularities and useJ-holomorphic curve techniques on the resolutions.

Scattering Resonances for Photonic Structures and Schrodinger Operators

Series
Applied and Computational Mathematics Seminar
Time
Monday, February 17, 2014 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Junshan LinAuburn University
Resonances are important in the study of transient phenomenaassociated with the wave equation, especially in understanding the largetime behavior of the solution to the wave equation when radiation lossesare small. In this talk, I will present recent studies on the scatteringresonances for photonic structures and Schrodinger operators. I will beginwith a study on the finite symmetric photoinc structure to illustrate theconvergence behavior of resonances. Then a general perturbation approachwill be introduced for the analysis of near bound-state resonances for bothcases. In particular, it is shown that, for a finite one dimensionalphotonic crystal with a defect, the near bound-state resonances converge tothe point spectrum of the infinite structure with an exponential rate whenthe number of periods increases. An analogous exponential decay rate alsoholds for the Schrodinger operator with a potential function that is alow-energy well surrounded by a thick barrier. The analysis also leads to asimple and accurate numerical approach to approximate the near bound-stateresonances. This is a joint work with Prof. Fadil Santosa in University ofMinnesota.

Pages