Previous PDE/GA seminars

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PDE and Geometric Analysis Seminar

The seminar will be held in room B115 of Van Vleck Hall on Mondays from 3:30pm - 4:30pm, unless indicated otherwise.


Seminar Schedule Spring 2011

date speaker title host(s)
Jan 24 Bing Wang (Princeton)
The Kaehler Ricci flow on Fano manifold 
Viaclovsky
Mar 15 (TUESDAY) at 4pm in B139 (joint wit Analysis) Francois Hamel (Marseille)
Optimization of eigenvalues of non-symmetric elliptic operators
Zlatos
Mar 28 Juraj Foldes (Vanderbilt)
Symmetry properties of parabolic problems and their applications
Zlatos
Apr 11 Alexey Cheskidov (UIC)
Navier-Stokes and Euler equations: a unified approach to the problem of blow-up
Kiselev
Date TBA Mikhail Feldman (UW Madison) TBA Local speaker
Date TBA Sigurd Angenent (UW Madison) TBA Local speaker

Seminar Schedule Fall 2010

date speaker title host(s)
Sept 13 Fausto Ferrari (Bologna)

Semilinear PDEs and some symmetry properties of stable solutions

Feldman
Sept 27 Arshak Petrosyan (Purdue)

Nonuniqueness in a free boundary problem from combustion

Feldman
Oct 7, Thursday, 4:30 pm, Room: 901 Van Vleck. Special day, time & room. Changyou Wang (U. of Kentucky)

Phase transition for higher dimensional wells

Feldman
Oct 11 Philippe LeFloch (Paris VI)

Kinetic relations for undercompressive shock waves and propagating phase boundaries

Feldman
Oct 29 Friday 2:30pm, Room: B115 Van Vleck. Special day, time & room. Irina Mitrea (IMA)

Boundary Value Problems for Higher Order Differential Operators

WiMaW
Nov 1 Panagiota Daskalopoulos (Columbia U)

Ancient solutions to geometric flows

Feldman
Nov 8 Maria Gualdani (UT Austin)

A nonlinear diffusion model in mean-field games

Feldman
Nov 18 Thursday 1:20pm Room: 901 Van Vleck Special day & time. Hiroshi Matano (Tokyo University)

Traveling waves in a sawtoothed cylinder and their homogenization limit

Angenent & Rabinowitz
Nov 29 Ian Tice (Brown University)

Global well-posedness and decay for the viscous surface wave problem without surface tension

Feldman
Dec. 8 Wed 2:25pm, Room: 901 Van Vleck. Special day, time & room. Hoai Minh Nguyen (NYU-Courant Institute)

Cloaking via change of variables for the Helmholtz equation

Feldman

Abstracts

Fausto Ferrari (Bologna)

Semilinear PDEs and some symmetry properties of stable solutions

I will deal with stable solutions of semilinear elliptic PDE's and some of their symmetry's properties. Moreover, I will introduce some weighted Poincaré inequalities obtained by combining the notion of stable solution with the definition of weak solution.

Arshak Petrosyan (Purdue)

Nonuniqueness in a free boundary problem from combustion

We consider a parabolic free boundary problem with a fixed gradient condition which serves as a simplified model for the propagation of premixed equidiffusional flames. We give a rigorous justification of an example due to J.L. V ́azquez that the initial data in the form of two circular humps leads to the nonuniqueness of limit solutions if the supports of the humps touch at the time of their maximal expansion.

This is a joint work with Aaron Yip.


Changyou Wang (U. of Kentucky)

Phase transition for higher dimensional wells

For a potential function [math]F[/math] that has two global minimum sets consisting of two compact connected Riemannian submanifolds in [math]\mathbb{R}^k[/math], we consider the singular perturbation problem:

Minimizing [math]\int \left(|\nabla u|^2+\frac{1}{\epsilon^2} F(u)\right)[/math] under given Dirichlet boundary data.

I will discuss a recent joint work with F.H.Lin and X.B.Pan on the asymptotic, as the parameter [math]\epsilon[/math] tends to zero, in terms of the area of minimal hypersurface interfaces, the minimal connecting energy, and the energy of minimizing harmonic maps into the phase manifolds under both Dirichlet and partially free boundary data. Our results in particular addressed the static case of the so-called Keller-Rubinstein-Sternberg problem.

Philippe LeFloch (Paris VI)

Kinetic relations for undercompressive shock waves and propagating phase boundaries

I will discuss the existence and properties of shock wave solutions to nonlinear hyperbolic systems that are small-scale dependent and, especially, contain undercompressive shock waves or propagating phase boundaries. Regularization-sensitive patterns often arise in continuum physics, especially in complex fluid flows. The so-called kinetic relation is introduced to characterize the correct dynamics of these nonclassical waves, and is tied to a higher-order regularization induced by a more complete model that takes into account additional small-scale physics. In the present lecture, I will especially explain the techniques of Riemann problems, Glimm-type scheme, and total variation functionals adapted to nonclassical shock waves.


Irina Mitrea

Boundary Value Problems for Higher Order Differential Operators

As is well known, many phenomena in engineering and mathematical physics can be modeled by means of boundary value problems for a certain elliptic differential operator L in a domain D.

When L is a differential operator of second order a variety of tools are available for dealing with such problems including boundary integral methods, variational methods, harmonic measure techniques, and methods based on classical harmonic analysis. The situation when the differential operator has higher order (as is the case for instance with anisotropic plate bending when one deals with fourth order) stands in sharp contrast with this as only fewer options could be successfully implemented. Alberto Calderon, one of the founders of the modern theory of Singular Integral Operators, has advocated in the seventies the use of layer potentials for the treatment of higher order elliptic boundary value problems. While the layer potential method has proved to be tremendously successful in the treatment of second order problems, this approach is insufficiently developed to deal with the intricacies of the theory of higher order operators. In fact, it is largely absent from the literature dealing with such problems.

In this talk I will discuss recent progress in developing a multiple layer potential approach for the treatment of boundary value problems associated with higher order elliptic differential operators. This is done in a very general class of domains which is in the nature of best possible from the point of view of geometric measure theory.


Panagiota Daskalopoulos (Columbia U)

Ancient solutions to geometric flows

We will discuss the clasification of ancient solutions to nonlinear geometric flows. It is well known that ancient solutions appear as blow up limits at a finite time singularity of the flow. Special emphasis will be given to the 2-dimensional Ricci flow. In this case we will show that ancient compact solution is either the Einstein (trivial) or one of the King-Rosenau solutions.

Maria Gualdani (UT Austin)

A nonlinear diffusion model in mean-field games

We present an overview of mean-field games theory and show recent results on a free boundary value problem, which models price formation dynamics. In such model, the price is formed through a game among infinite number of agents. Existence and regularity results, as well as linear stability, will be shown.

Hiroshi Matano (Tokyo University)

Traveling waves in a sawtoothed cylinder and their homogenization limit

My talk is concerned with a curvature-dependent motion of plane curves in a two-dimensional cylinder with spatially undulating boundary. In other words, the boundary has many bumps and we assume that the bumps are aligned in a spatially recurrent manner.

The goal is to study how the average speed of the traveling wave depends on the geometry of the domain boundary. More specifically, we consider the homogenization problem as the boundary undulation becomes finer and finer, and determine the homogenization limit of the average speed and the limit profile of the traveling waves. Quite surprisingly, this homogenized speed depends only on the maximal opening angles of the domain boundary and no other geometrical features are relevant.

Next we consider the special case where the boundary undulation is quasi-periodic with m independent frequencies. We show that the rate of convergence to the homogenization limit depends on this number m.

This is joint work with Bendong Lou and Ken-Ichi Nakamura.

Ian Tice (Brown University)

Global well-posedness and decay for the viscous surface wave problem without surface tension

We study the incompressible, gravity-driven Navier-Stokes equations in three dimensional domains with free upper boundaries and fixed lower boundaries, in both the horizontally periodic and non-periodic settings. The effect of surface tension is not included. We employ a novel two-tier nonlinear energy method that couples the boundedness of certain high-regularity norms to the algebraic decay of lower-regularity norms. The algebraic decay allows us to balance the growth of the highest order derivatives of the free surface function, which then allows us to derive a priori estimates for solutions. We then prove local well-posedness in our energy space, which yields global well-posedness and decay. The novel LWP theory is established through the study of the linear Stokes problem in moving domains. This is joint work with Yan Guo.


Hoai Minh Nguyen (NYU-Courant Institute)

Cloaking via change of variables for the Helmholtz equation

A region of space is cloaked for a class of measurements if observers are not only unaware of its contents, but also unaware of the presence of the cloak using such measurements. One approach to cloaking is the change of variables scheme introduced by Greenleaf, Lassas, and Uhlmann for electrical impedance tomography and by Pendry, Schurig, and Smith for the Maxwell equation. They used a singular change of variables which blows up a point into the cloaked region. To avoid this singularity, various regularized schemes have been proposed. In this talk I present results related to cloaking via change of variables for the Helmholtz equation using the natural regularized scheme introduced by Kohn, Shen, Vogelius, and Weintein, where the authors used a transformation which blows up a small ball instead of a point into the cloaked region. I will discuss the degree of invisibility for a finite range or the full range of frequencies, and the possibility of achieving perfect cloaking. If time permits, I will mention some results related to the wave equation.

Bing Wang (Princeton)

The Kaehler Ricci flow on Fano manifold

We show the convergence of the Kaehler Ricci flow on every 2-dimensional Fano manifold which admits big [math]\alpha_{\nu, 1}[/math] or [math]\alpha_{\nu, 2}[/math] (Tian's invariants). Our method also works for 2-dimensional Fano orbifolds. Since Tian's invariants can be calculated by algebraic geometry method, our convergence theorem implies that one can find new Kaehler Einstein metrics on orbifolds by calculating Tian's invariants. An essential part of the proof is to confirm the Hamilton-Tian conjecture in complex dimension 2.

Francois Hamel (Marseille)

Optimization of eigenvalues of non-symmetric elliptic operators

The talk is concerned with various optimization results for the principal eigenvalues of general second-order elliptic operators in divergence form with Dirichlet boundary condition in bounded domains of [math]R^n[/math]. To each operator in a given domain, we can associate a radially symmetric operator in the ball with the same Lebesgue measure, with a smaller principal eigenvalue. The constraints on the coefficients are of integral, pointwise or geometric types. In particular, we generalize the Rayleigh-Faber-Krahn inequality for the principal eigenvalue of the Dirichlet Laplacian. The proofs use a new symmetrization technique, different from the Schwarz symmetrization. This talk is based on a joint work with N. Nadirashvili and E. Russ.

Juraj Foldes (Vanderbilt)

Symmetry properties of parabolic problems and their applications

Positive solutions of nonlinear parabolic problems can have a very complex behavior. However, assuming certain symmetry conditions, it is possible to prove that the solutions converge to the space of symmetric functions. We show that this property is 'stable'; more specifically if the symmetry conditions are replaced by asymptotically symmetric ones, the solutions still approach the space of symmetric functions. As an application, we show new results on convergence of solutions to a single equilibrium.

Alexey Cheskidov (UIC)

Navier-Stokes and Euler equations: a unified approach to the problem of blow-up

The problems of blow-up for Navier-Stokes and Euler equations have been extensively studied for decades using different techniques. Motivated by Kolmogorov's theory of turbulence, we present a new unified approach to the blow-up problem for the equations of incompressible fluid motion. In particular, we present a new regularity criterion which is weaker than the Beale-Kato-Majda condition in the inviscid case, and weaker than every Ladyzhenskaya-Prodi-Serrin condition in the viscous case.