Seminars and Colloquia by Series

Series: PDE Seminar
Tuesday, November 20, 2012 - 15:05 , Location: Skiles 006 , Rafael de la Llave , Georgia Tech , Organizer: Zhiwu Lin
We prove an a-posteriori KAM theorem which applies to some ill-posed Hamiltonian equations. We show that given an approximate solution of an invariance equation which also satisfies some non-degeneracy conditions, there is a true solution nearby. Furthermore, the solution is "whiskered" in the sense that it has stable and unstable directions. We do not assume that the equation defines an evolution equation. Some examples are the Boussinesq equation (and system) and the elliptic equations in cylindrical domains. This is joint work with Y. Sire. Related work with E. Fontich and Y. Sire.
Series: PDE Seminar
Tuesday, November 13, 2012 - 15:05 , Location: Skiles 006 , Ming Chen , University of Pittsburgh , Organizer: Zhiwu Lin
We prove via explicitly constructed initial data that solutionsto the gravity-capillary wave system in R^3 representing a 2d air-waterinterface immediately fail to be C^3 with respect to the initial data ifthe initial (h_0, \psi_0) \in H^{s + 1/2} \times H^s for s<3, where h isthe free surface and \psi is the velocity potential.
Series: PDE Seminar
Tuesday, November 6, 2012 - 15:01 , Location: Skiles 006 , Professor Ronghua Pan , Georgia Tech , panrh@math.gatech.edu , Organizer: Ronghua Pan
From its physical origin, the viscosity and heat conductivity in compressible fluids depend on absolute temperature through power laws. The mathematical theory on the well-posedness and regularity on this setting is widely open. I will report some recent progress made on this direction, with emphasis on the lower bound of temperature, and global existence of solutions in one or multiple dimensions. The relation between thermodynamics laws and Navier-Stokes equations will also be discussed. This talk is based on joint works with Weizhe Zhang.
Series: PDE Seminar
Tuesday, October 23, 2012 - 15:05 , Location: Skiles 006 , Alexander Kiselev , Department of Mathematics, University of Wisconsin, Madison , Organizer: Zhiwu Lin
Active scalars appear in many problems of fluid dynamics. The most common examples of active scalar equations are 2D Euler, Burgers, and 2D surface quasi-geostrophic (SQG) equations. Many questions about regularity and properties of solutions of these equations remain open. I will discuss the recently introduced idea of nonlocal maximum principle, which helped prove global regularity of solutions to the critical SQG equation. I will describe some further recent developments on regularity and blowup of solutions to active scalar equations.
Series: PDE Seminar
Tuesday, October 9, 2012 - 15:05 , Location: Skiles 006 , Roman Shvydkoy , University of Illinois at Chicago , Organizer: Zhiwu Lin
The existence of self-similar blow-up for the viscous incompressible fluids was a classical question settled in the seminal of works of Necas, et al and Tsai in the 90'. The corresponding scenario for the inviscid Euler equations has not received as much attention, yet it appears in many numerical simulations, for example those based on vortex filament models of Kida's high symmetry flows. The case of a homogeneous self-similar profile is especially interesting due to its relevance to other theoretical questions such the Onsager conjecture or existence of Landau type solutions. In this talk we give an account of recent studies demonstrating that a self-similar blow-up is unsustainable the Euler system under various weak decay assumptions on the profile. We will also talk about general energetics of the Euler system that, in part, is responsible for such exclusion results.
Series: PDE Seminar
Monday, October 8, 2012 - 16:05 , Location: Skiles 006 , Christoph Walker , University of Hannover, Germany , Organizer: Zhiwu Lin
The talk focuses on positive equilibrium (i.e. time-independent)solutionsto mathematical models for the dynamics of populations structured by ageand spatial position. This leads to the study of quasilinear parabolicequations with nonlocal and possibly nonlinear initial conditions. Weshallsee in an abstract functional analytic framework how bifurcationtechniquesmay be combined with optimal parabolic regularity theory to establishtheexistence of positive solutions. As an application of these results wegivea description of the geometry of coexistence states in a two-parameterpredator-prey model.
Series: PDE Seminar
Tuesday, October 2, 2012 - 15:05 , Location: Skiles 006 , S. S. Sritharan , Naval Postgraduate School, Monterey, California , Organizer: Zhiwu Lin
In this talk we will give a very elementary explanation of issues associated with the unique global solvability of three dimensional Navier-Stokes equation and then discuss various modifications of the classical system for which the unique solvability is resolved. We then discuss some of the fascinating issues associated with the stochastic Navier-Stokes equations such as Gaussian & Levy Noise, large deviations and invariant measures.
Series: PDE Seminar
Tuesday, September 25, 2012 - 15:05 , Location: Skiles 006 , Meijun Zhu , University of Oklahoma , Organizer: Zhiwu Lin
We shall describe our recent work on the extension of sharp Hardy-Littlewood-Sobolev inequality, including the reversed HLS inequality with negative exponents. The background and motivation will be given. The related integral curvature equations may be discussed if time permits.
Series: PDE Seminar
Tuesday, September 18, 2012 - 15:05 , Location: Skiles 006 , Bin Cheng , Arizona State University , Organizer: Zhiwu Lin
Time-averages are common observables in analysis of experimental data and numerical simulations of physical systems. We describe a PDE-theoretical framework for studying time-averages of dynamical systems that evolve in both fast and slow scales. Patterns arise upon time-averaging, which in turn affects long term dynamics via nonlinear coupling. We apply this framework to geophysical fluid dynamics in spherical and bounded domains subject to strong Coriolis force and/or Lorentz force.
Series: PDE Seminar
Tuesday, September 4, 2012 - 15:05 , Location: Skiles 006 , Zhaoyang Yin , Sun Yat-sen University, China , Organizer: Zhiwu Lin
In this talk, we consider the Cauchy problem of a modified two-component Camassa-Holm shallow water system. We first establish local well-possedness of the Cauchy problem of the system. Then we present several blow-up results of strong solutions to the system. Moreover, we show the existence of global weak solutions to the system. Finally, we address global conservative solutions to the system. This talk is based on several joint works with C. Guan, K. H. Karlsen, K. Yan and W. Tan.

Pages