Events
Stanislaw Szarek, Case Western Reserve University/Sorbonne Université
ZoomZoom ID: 936 5420 1948 Password: the last four digits of the Zoom ID in reverse order
Hussam Al Daas, STFC, Rutherford Appleton Laboratory, Two-level Nyström—Schur preconditioner for symmetric positive definite matrices
ZoomRandomized methods are becoming increasingly popular in numerical linear algebra. However, few attempts have been made to use them in developing preconditioners. Our interest lies in solving large-scale sparse symmetric positive definite linear systems of equations where the system matrix is preordered to doubly bordered block diagonal form (for example, using a nested dissection ordering).…
Alessio Porretta, Università di Roma Tor Vergata, Long time behavior in mean field game systems
ZoomMean field game PDE systems were introduced by J-M. Lasry and P.-L. Lions to describe Nash equilibria in multi-agents dynamic optimization. In the simplest model, those are forward-backward systems coupling Hamilton-Jacobi with Fokker-Planck equations. In this talk I will discuss the long time behavior of second order systems in the periodic case under suitable stability…
Dustin Kapraun, EPA, SIAM Mathematics in Industry Series
ZoomDustin Kapraun attained degrees in mathematics (B.S., 1998), physics (M.S., 2002), and applied mathematics (Ph.D., 2014), all from North Carolina State University. After finishing the Ph.D., he completed two postdoctoral research appointments at the U.S. Environmental Protection Agency (EPA) National Center for Computational Toxicology, during which he developed physiologically based pharmacokinetic (PBPK) models for human…
Vishesh Jain, Stanford University, On the real Davies’ conjecture
ZoomWe show that every $n \times n$ real matrix $A$ is within distance $\delta \|A\|$ in the operator norm of an $n\times n$ real matrix $A'$ whose eigenvectors have condition number $\tilde{O}(\text{poly}(n)/\delta)$. In fact, we show that with high probability, an additive i.i.d. sub-Gaussian perturbation of $A$ has this property. Up to log factors, this…
GaYee Park, University of Massachusetts Amherst, Naruse hook formula for linear extensions of mobile posets
ZoomLinear extensions of posets are important objects in enumerative and algebraic combinatorics that are difficult to count in general. Families of posets like straight shapes and $d$-complete posets have hook-length product formulas to count linear extensions, whereas families like skew shapes have determinant or positive sum formulas like the Naruse hook length formula from 2014.…
Barbara Kaltenbacher, University of Klagenfurt, Some Asymptotics of Equations in Nonlinear Acoustics
ZoomHigh intensity (focused) ultrasound HIFU is used in numerous medical and industrial applications ranging from lithotripsy and thermotherapy via ultrasound cleaning and welding to sonochemistry. The relatively high amplitudes arising in these applications necessitate modeling of sound propagation via nonlinear wave equations and in this talk we will first of all dwell on this modeling aspect. Then…
Orsola Capovilla-Searle, Duke, Infinitely many Lagrangian Tori in Milnor fibers constructed via Lagrangian Fillings of Legendrian links
ZoomOne approach to studying symplectic manifolds with contact boundary is to consider Lagrangian submanifolds with Legendrian boundary; in particular, one can study exact Lagrangian fillings of Legendrian links. There are still many open questions on the spaces of exact Lagrangian fillings of Legendrian links in the standard contact 3-sphere, and one can use Floer theoretic…
Dylan Bates, NC State, Machine Learning: My First Neural Networks
ZoomMachine learning has blown up in popularity in the past decade, with applications from healthcare to self-driving cars, being used to create art, play video games, and act as customer service representatives. One of the most common and useful tools for these applications are neural networks: universal function approximators. This interactive workshop is meant for…
Alan Edelman, Massachusetts Institute of Technology, 53 Matrix Factorizations and Random Matrix Theory
ZoomIn this “something for everyone” talk, we will place the matrix decompositions that are so valuable in all fields of computation in a historical abstract context. It is well known that the singular value decomposition was discussed as far back as the 19th century by Beltrami and Jordan. Lesser known is that Cartan had a blueprint…
Sarah Peluse, Princeton University/IAS, On the polynomial Szemer\’edi theorem and related results
ZoomIn this talk, I'll survey recent progress on problems in additive combinatorics, harmonic analysis, and ergodic theory related to Bergelson and Leibman's polynomial generalization of Szemer\'edi's theorem. Zoom ID: 980 3116 7550 Passcode: last 4 digits of the Zoom ID in reverse order
Jérôme Bolte, Université Toulouse 1 Capitole, A Bestiary of Counterexamples in Smooth Convex Optimization
ZoomCounterexamples to some old-standing optimization problems in the smooth convex coercive setting are provided. Block-coordinate, steepest descent with exact search or Bregman descent methods do not generally converge. Other failures of various desirable features are established: directional convergence of Cauchy’s gradient curves, convergence of Newton’s flow, finite length of Tikhonov path, convergence of central paths,…
Andrea Klaiber-Langen and Vakhtang Putkaradze from ATCO
ZoomCongratulations, you are graduating with a PhD! You have done fantastic work in your thesis and are ready to take on the world. What is going to happen now? Should you go to industry or academia? You probably heard a lot about both job choices. In this lecture, the speakers, Andrea Klaiber-Langen and Vakhtang Putkaradze,…
Teemu Saksala, NC State, Stable reconstruction of simple Riemannian manifolds from unknown interior sources
ZoomConsider the geometric inverse problem: There is a set of delta-sources in spacetime that emit waves travelling at unit speed. If we know all the arrival times at the boundary cylinder of the spacetime, can we reconstruct the space, a Riemannian manifold with boundary? With a finite set of sources we can only hope to…
Pratik Misra, NC State, Combinatorial problems on trees and graphical models
ZoomChair: Seth Sullivant (smsulli2@ncsu.edu, contact for Zoom access)
Alban Quadrat, Sorbonne University, Paris, France, An introduction to the Quillen-Suslin theorem: algorithms and applications
ZoomIn 1955, Serre conjectured that every row vector with entries in a commutative polynomial ring R=k over a field k, admitting a right inverse over R, could be completed into a square matrix whose determinant is 1. That conjecture was independently proved by Quillen and Suslin in 1976 and is nowadays called the Quillen-Suslin theorem.…