Previous PDE/GA seminars
Click here for the current PDE and Geometric Analysis seminar schedule.
Contents
 1 PDE GA Seminar Schedule Spring 2017
 2 PDE GA Seminar Schedule Fall 2016
 3 Seminar Schedule Spring 2016
 4 Seminar Schedule Fall 2015
 5 Seminar Schedule Spring 2015
 6 Seminar Schedule Fall 2014
 7 Seminar Schedule Spring 2014
 8 Seminar Schedule Fall 2013
 9 Seminar Schedule Spring 2013
 10 Seminar Schedule Fall 2012
 11 Seminar Schedule Spring 2012
 12 Seminar Schedule Fall 2011
 13 Seminar Schedule Spring 2011
 14 Seminar Schedule Fall 2010
 15 Abstracts
 15.1 Daniel Spirn
 15.2 Donghyun Lee
 15.3 Kevin Zumbrun
 15.4 Will Feldman
 15.5 Ryan Hynd
 15.6 GungMin Gie
 15.7 Tau Shean Lim
 15.8 Tarek M. ELgindi
 15.9 Adrian Tudorascu
 15.10 Alexis Vasseur
 15.11 MinhBinh Tran
 15.12 David Kaspar
 15.13 Brian Weber
 15.14 Tianling Jin
 15.15 Russell Schwab
 15.16 Jingrui Cheng
 15.17 Paul Rabinowitz
 15.18 Hong Zhang
 15.19 Aaron Yip
 15.20 Hiroyoshi Mitake
 15.21 Nestor Guillen
 15.22 Ryan Denlinger
 15.23 Misha Feldman
 15.24 Jessica Lin
 15.25 Sergey Bolotin
 15.26 MoonJin Kang
 15.27 Hung Tran
 15.28 Eric Baer
 15.29 Donghyun Lee
 15.30 HyungJu Hwang
 15.31 MinhBinh Tran
 15.32 Bob Jensen
 15.33 Luis Silvestre
 15.34 Connor Mooney
 15.35 Javier Gomez Serrano
 15.36 Yifeng Yu
 15.37 Nam Le
 15.38 Qin Li
 15.39 Lu Wang
 15.40 Christophe Lacave
 15.41 Jun Kitagawa (Toronto)
 15.42 Jessica Lin (Madison)
 15.43 Yaguang Wang (Shanghai Jiao Tong)
 15.44 Benoit Pausader (Princeton)
 15.45 Haozhao Li (University of Science and Technology of China)
 15.46 Jennifer Beichman (UWMadison)
 15.47 Ben Fehrman (University of Chicago)
 15.48 Vera Hur
 15.49 SungJin Oh
 15.50 Yuan Lou
 15.51 Diego Cordoba
 15.52 Greg Kuperberg
 15.53 Steve Hofmann
 15.54 Xiangwen Zhang
 15.55 Xuwen Chen
 15.56 Kyudong Choi
 15.57 Myoungjean Bae
 15.58 Philip Isett
 15.59 Lei Wu
 15.60 Xuan Hien Nguyen
 15.61 Greg Drugan (U. of Washington)
 15.62 Guo Luo (Caltech)
 15.63 Xiaojie Wang(Stony Brook)
 15.64 Roman Shterenberg(UAB)
 15.65 Antonio Ache(Princeton)
 15.66 JeanMichel Roquejoffre (Toulouse)
 15.67 Myoungjean Bae (POSTECH)
 15.68 Changhui Tan (University of Maryland)
 15.69 Hongjie Dong (Brown University)
 15.70 Hao Jia (University of Chicago)
 15.71 Alexander Pushnitski (King's College)
 15.72 Ronghua Pan (Georgia Tech)
 15.73 Myoungjean Bae (POSTECH)
 15.74 Mike Cullen (Met. Office, UK)
 15.75 Mohammad Ghomi(Math. Georgia Tech)
 15.76 Wei Xiang (Oxford)
 15.77 Adrian Tudorascu (West Virginia University)
 15.78 Diego Cordoba (Madrid)
 15.79 Fausto Ferrari (Bologna)
 15.80 Arshak Petrosyan (Purdue)
 15.81 Changyou Wang (U. of Kentucky)
 15.82 Philippe LeFloch (Paris VI)
 15.83 Irina Mitrea
 15.84 Panagiota Daskalopoulos (Columbia U)
 15.85 Maria Gualdani (UT Austin)
 15.86 Hiroshi Matano (Tokyo University)
 15.87 Ian Tice (Brown University)
 15.88 Hoai Minh Nguyen (NYUCourant Institute)
 15.89 Bing Wang (Princeton)
 15.90 Francois Hamel (Marseille)
 15.91 Juraj Foldes (Vanderbilt)
 15.92 Alexey Cheskidov (UIC)
 15.93 Takis Souganidis (Chicago)
 15.94 Scott Armstrong (UWMadison)
 15.95 Russell Schwab (Carnegie Mellon)
 15.96 Valentin Ovsienko (University of Lyon)
 15.97 Adrian Tudorascu (West Virginia University)
 15.98 James Nolen (Duke)
 15.99 Betsy Stovall (UCLA)
 15.100 Charles Smart (MIT)
 15.101 Yao Yao (UCLA)
 15.102 Xuan Hien Nguyen (Iowa State)
 15.103 Nestor Guillen (UCLA)
 15.104 Charles Smart (MIT)
 15.105 Vlad Vicol (University of Chicago)
 15.106 Jiahong Wu (Oklahoma State)
 15.107 Joana Oliveira dos Santos Amorim (Universit\'e Paris Dauphine)
 15.108 GuiQiang Chen (Oxford)
 15.109 Jacob GlennLevin (UT Austin)
 15.110 Bing Wang (UW Madison)
 15.111 Peter Polacik (University of Minnesota)
 15.112 Kyudong Choi (UW Madison)
 15.113 Yao Yao (UW Madison)
 15.114 Myoungjean Bae (POSTECH)
PDE GA Seminar Schedule Spring 2017
date  speaker  title  host(s) 

January 23 Special time and location: 33:50pm, B325 Van Vleck 
Sigurd Angenent (UW)  Ancient convex solutions to Mean Curvature Flow  Kim & Tran 
January 30  Serguei Denissov (UW)  Instability in 2D Euler equation of incompressible inviscid fluid  Kim & Tran 
February 6  Wasow lecture  Benoit Perthame (University of Paris VI)  Jin  
February 13  Bing Wang (UW)  The extension problem of the mean curvature flow  Kim & Tran 
February 20  Eric Baer (UW)  Isoperimetric sets inside almostconvex cones  Kim & Tran 
February 27  Ben Seeger (University of Chicago)  Homogenization of pathwise HamiltonJacobi equations  Tran 
March 7  Mathematics Department Distinguished Lecture  Roger Temam (Indiana University)  On the mathematical modeling of the humid atmosphere  Smith 
March 8  Analysis/Applied math/PDE seminar  Roger Temam (Indiana University)  Weak solutions of the ShigesadaKawasakiTeramoto system  Smith 
March 13  Sona Akopian (UTAustin)  Global $L^p$ well posedness of the Boltzmann equation with an anglepotential concentrated collision kernel.  Kim 
March 27  Analysis/PDE seminar  Sylvia Serfaty (Courant)  MeanField Limits for GinzburgLandau vortices  Tran 
March 29  Wasow lecture  Sylvia Serfaty (Courant)  Microscopic description of Coulombtype systems 

March 30 Special day (Thursday) and location: B139 Van Vleck 
GuiQiang Chen (Oxford)  Supersonic Flow onto Solid Wedges,  Feldman

April 3  Zhenfu Wang (Maryland)  Mean field limit for stochastic particle systems with singular forces  Kim 
April 10  Andrei Tarfulea (Chicago)  Improved estimates for thermal fluid equations  Baer 
April 17 Special time and location: 33:50pm, B219 Van Vleck 
SiaoHao Guo (Rutgers)  Analysis of Velázquez's solution to the mean curvature flow with a type II singularity  Lu Wang

April 24  Jianfeng Lu (Duke)  Evolution of crystal surfaces: from mesoscopic to continuum models  Li 
April 25 joint Analysis/PDE seminar  Chris Henderson (Chicago)  A localintime Harnack inequality and applications to reactiondiffusion equations  Lin 
May 1st(Special time: 4:005:00pm)  Jeffrey Streets (UCIrvine)  Generalized Kahler Ricci flow and a generalized Calabi conjecture  Bing Wang 
PDE GA Seminar Schedule Fall 2016
date  speaker  title  host(s) 

September 12  Daniel Spirn (U of Minnesota)  Dipole Trajectories in BoseEinstein Condensates  Kim 
September 19  Donghyun Lee (UWMadison)  The Boltzmann equation with specular boundary condition in convex domains  Feldman 
September 26  Kevin Zumbrun (Indiana)  A Stable Manifold Theorem for a class of degenerate evolution equations  Kim 
October 3  Will Feldman (UChicago )  Liquid Drops on a Rough Surface  Lin & Tran 
October 10  Ryan Hynd (UPenn)  Extremal functions for Morrey’s inequality in convex domains  Feldman 
October 17  GungMin Gie (Louisville)  Boundary layer analysis of some incompressible flows  Kim 
October 24  Tau Shean Lim (UW Madison)  Traveling Fronts of ReactionDiffusion Equations with Ignition Media and Levy Operators  Kim & Tran 
October 31 (Special time and room: B313VV, 3PM4PM)  Tarek Elgindi ( Princeton)  Propagation of Singularities in Incompressible Fluids  Lee & Kim 
November 7  Adrian Tudorascu (West Virginia)  HamiltonJacobi equations in the Wasserstein space of probability measures  Feldman 
November 14  Alexis Vasseur ( UTAustin)  Compressible NavierStokes equations with degenerate viscosities  Feldman 
November 21  MinhBinh Tran (UW Madison )  Quantum Kinetic Problems  Hung Tran 
November 28  David Kaspar (Brown)  Kinetics of shock clustering  Tran 
December 5 (Special time and room: 3PM4PM, B313VV)  Brian Weber (University of Pennsylvania)  DegenerateElliptic PDE and Toric Kahler 4manfiolds  Bing Wang 
December 12  (no seminar) 
Seminar Schedule Spring 2016
date  speaker  title  host(s) 

January 25  Tianling Jin (HKUST and Caltech)  Holder gradient estimates for parabolic homogeneous pLaplacian equations  Zlatos 
February 1  Russell Schwab (Michigan State University)  Neumann homogenization via integrodifferential methods  Lin 
February 8  Jingrui Cheng (UW Madison)  Semigeostrophic system with variable Coriolis parameter  Tran & Kim 
February 15  Paul Rabinowitz (UW Madison)  On A Double Well Potential System  Tran & Kim 
February 22  Hong Zhang (Brown)  On an elliptic equation arising from composite material  Kim 
February 29  Aaron Yip (Purdue university)  Discrete and Continuous Motion by Mean Curvature in Inhomogeneous Media  Tran 
March 7  Hiroyoshi Mitake (Hiroshima university)  Selection problem for fully nonlinear equations  Tran 
March 15  Nestor Guillen (UMass Amherst)  Minmax formulas for integrodifferential equations and applications  Lin 
March 21 (Spring Break)  
March 28  Ryan Denlinger (Courant Institute)  The propagation of chaos for a rarefied gas of hard spheres in vacuum  Lee 
April 4  No seminar  
April 11  Misha Feldman (UW)  Shock reflection, free boundary problems and degenerate elliptic equations  
April 14: 2:25 PM in VV 901Joint with Probability Seminar  Jessica Lin (UWMadison)  Optimal Quantitative Error Estimates in Stochastic Homogenization for Elliptic Equations in Nondivergence Form  
April 18  Sergey Bolotin (UWMadison)  Degenerate billiards  
April 2124, KINet conference: Boundary Value Problems and Multiscale Coupling Methods for Kinetic Equations  Link: http://www.kinet.umd.edu/content/conf?event_id=493  
April 25  MoonJin Kang (UTAustin)  On contraction of large perturbation of shock waves, and inviscid limit problems  Kim 
Tuesday, May 3, 4:00 p.m., in B139 (Joint AnalysisPDE seminar )  Stanley Snelson (University of Chicago)  Seeger & Tran.  
May 1620, Conference in Harmonic Analysis in Honor of Michael Christ  Link: https://www.math.wisc.edu/ha_2016/ 
Seminar Schedule Fall 2015
Seminar Schedule Spring 2015
Seminar Schedule Fall 2014
Seminar Schedule Spring 2014
date  speaker  title  host(s) 

January 14 at 4pm in B139 (TUESDAY), joint with Analysis  JeanMichel Roquejoffre (Toulouse)  Zlatos  
February 10  Myoungjean Bae (POSTECH)  Feldman  
February 24  Changhui Tan (Maryland) 
Global classical solution and long time behavior of macroscopic flocking models. 
Kiselev 
March 3  Hongjie Dong (Brown)  Kiselev  
March 10  Hao Jia (University of Chicago)  Kiselev  
March 31  Alexander Pushnitski (King's College London)  Kiselev  
April 21  Ronghua Pan (Georgia Tech) 
Compressible NavierStokesFourier system with temperature dependent dissipation. 
Kiselev 
Seminar Schedule Fall 2013
myeongju Chaedate  speaker  title  host(s) 

September 9  Greg Drugan (U. of Washington) 
Construction of immersed selfshrinkers 
Angenent 
October 7  Guo Luo (Caltech) 
Potentially Singular Solutions of the 3D Incompressible Euler Equations. 
Kiselev 
November 18  Roman Shterenberg (UAB) 
Recent progress in multidimensional periodic and almostperiodic spectral problems. 
Kiselev 
November 25  Myeongju Chae (Hankyong National University visiting UW)  Kiselev  
December 2  Xiaojie Wang  Wang  
December 16  Antonio Ache(Princeton)  Viaclovsky 
Seminar Schedule Spring 2013
date  speaker  title  host(s) 

February 4  Myoungjean Bae (POSTECH) 
Transonic shocks for EulerPoisson system and related problems 
Feldman 
February 18  Mike Cullen (Met. Office, UK) 
Modelling the uncertainty in predicting largescale atmospheric circulations. 
Feldman 
March 18  Mohammad Ghomi(Math. Georgia Tech)  Angenent  
April 8  Wei Xiang (Oxford) 
Shock Diffraction Problem to the Two Dimensional Nonlinear Wave System and Potential Flow Equation. 
Feldman 
Thursday April 25, Time: 3:30, Room: 901 Van Vleck (Note: Special Day, Room)  Adrian Tudorascu (West Virginia University)  Onedimensional pressureless  Feldman 
May 6  Diego Cordoba (Madrid)  Kiselev 
Seminar Schedule Fall 2012
date  speaker  title  host(s) 

September 17  Bing Wang (UW Madison) 
On the regularity of limit space 
local 
October 15  Peter Polacik (University of Minnesota) 
Exponential separation between positive and signchanging solutions and its applications 
Zlatos 
November 26  Kyudong Choi (UW Madison) 
Estimates on fractional higher derivatives of weak solutions for the NavierStokes equations 
local 
December 10  Yao Yao (UW Madison) 
Confinement for nonlocal interaction equation with repulsiveattractive kernels 
local 
Seminar Schedule Spring 2012
date  speaker  title  host(s) 

Feb 6  Yao Yao (UCLA) 
Degenerate diffusion with nonlocal aggregation: behavior of solutions 
Kiselev 
March 12  Xuan Hien Nguyen (Iowa State) 
Gluing constructions for solitons and selfshrinkers under mean curvature flow 
Angenent 
March 21(Wednesday!), Room 901 Van Vleck  Nestor Guillen (UCLA)  Feldman  
March 26  Vlad Vicol (University of Chicago) 
Shape dependent maximum principles and applications 
Kiselev 
April 9  Charles Smart (MIT)  Seeger  
April 16  Jiahong Wu (Oklahoma) 
The 2D Boussinesq equations with partial dissipation 
Kiselev 
April 23  Joana Oliveira dos Santos Amorim (Universite Paris Dauphine) 
A geometric look on AubryMather theory and a theorem of Birkhoff 
Bolotin 
April 27 (Colloquium. Friday at 4pm, in Van Vleck B239)  GuiQiang Chen (Oxford) 
Nonlinear Partial Differential Equations of Mixed Type 
Feldman 
May 14  Jacob GlennLevin (UT Austin) 
Incompressible Boussinesq equations in borderline Besov spaces 
Kiselev 
Seminar Schedule Fall 2011
date  speaker  title  host(s) 

Oct 3  Takis Souganidis (Chicago) 
Stochastic homogenization of the Gequation 
Armstrong 
Oct 10  Scott Armstrong (UWMadison) 
Partial regularity for fully nonlinear elliptic equations 
Local speaker 
Oct 17  Russell Schwab (Carnegie Mellon) 
On AleksandrovBakelmanPucci type estimates for integrodifferential equations (comparison theorems with measurable ingredients) 
Armstrong 
October 24 ( with Geometry/Topology seminar)  Valentin Ovsienko (University of Lyon)  Marí Beffa  
Oct 31  Adrian Tudorascu (West Virginia University) 
Weak Lagrangian solutions for the SemiGeostrophic system in physical space 
Feldman 
Nov 7  James Nolen (Duke)  Armstrong  
Nov 21 (Joint with Analysis seminar)  Betsy Stovall (UCLA) 
Scattering for the cubic KleinGordon equation in two dimensions 
Seeger 
Dec 5  Charles Smart (MIT) 
Optimal Lipschitz Extensions and Regularity for the Infinity Laplacian 
Armstrong 
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 nonsymmetric elliptic operators 
Zlatos 
Mar 28  Juraj Foldes (Vanderbilt) 
Symmetry properties of parabolic problems and their applications 
Zlatos 
Apr 11  Alexey Cheskidov (UIC) 
NavierStokes and Euler equations: a unified approach to the problem of blowup 
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)  Feldman  
Oct 7, Thursday, 4:30 pm, Room: 901 Van Vleck. Special day, time & room.  Changyou Wang (U. of Kentucky)  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)  Feldman  
Nov 8  Maria Gualdani (UT Austin)  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 wellposedness 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 (NYUCourant Institute)  Feldman 
Abstracts
Daniel Spirn
Dipole Trajectories in BoseEinstein Condensates
BoseEinstein condensates (BEC) are a state of matter in which supercooled atoms condense into the lowest possible quantum state. One interesting important feature of BECs are the presence of vortices that form when the condensate is stirred with lasers. I will discuss the behavior of these vortices, which interact with both the confinement potential and other vortices. I will also discuss a related inverse problem in which the features of the confinement can be extracted by the propagation of vortex dipoles.
Donghyun Lee
The Boltzmann equation with specular reflection boundary condition in convex domains
I will present a recent work (https://arxiv.org/abs/1604.04342) with Chanwoo Kim on the globalwellposedness and stability of the Boltzmann equation in general smooth convex domains.
Kevin Zumbrun
TITLE: A Stable Manifold Theorem for a class of degenerate evolution equations
ABSTRACT: We establish a Stable Manifold Theorem, with consequent exponential decay to equilibrium, for a class
of degenerate evolution equations $Au'+u=D(u,u)$ with A bounded, selfadjoint, and onetoone, but not invertible, and
$D$ a bounded, symmetric bilinear map. This is related to a number of other scenarios investigated recently for which the
associated linearized ODE $Au'+u=0$ is illposed with respect to the Cauchy problem. The particular case studied here
pertains to the steady Boltzmann equation, yielding exponential decay of largeamplitude shock and boundary layers.
Will Feldman
Liquid Drops on a Rough Surface
I will discuss the problem of determining the minimal energy shape of a liquid droplet resting on a rough solid surface. The shape of a liquid drop on a solid is strongly affected by the microstructure of the surface on which it rests, where the surface inhomogeneity arises through varying chemical composition and surface roughness. I will explain a macroscopic regularity theory for the free boundary which allows to study homogenization, and more delicate properties like the size of the boundary layer induced by the surface roughness.
The talk is based on joint work with Inwon Kim. A remark for those attending the weekend conference: this talk will attempt to have as little as possible overlap with I. Kim's conference talks.
Ryan Hynd
Extremal functions for Morrey’s inequality in convex domains
A celebrated result in the theory of Sobolev spaces is Morrey's inequality, which establishes the continuous embedding of the continuous functions in certain Sobolev spaces. Interestingly enough the equality case of this inequality has not been thoroughly investigated (unless the underlying domain is R^n). We show that if the underlying domain is a bounded convex domain, then the extremal functions are determined up to a multiplicative factor. We will explain why the assertion is false if convexity is dropped and why convexity is not necessary for this result to hold.
GungMin Gie
Boundary layer analysis of some incompressible flows
The motions of viscous and inviscid fluids are modeled respectively by the NavierStokes and Euler equations. Considering the NavierStokes equations at vanishing viscosity as a singular perturbation of the Euler equations, one major problem, still essentially open, is to verify if the NavierStokes solutions converge as the viscosity tends to zero to the Euler solution in the presence of physical boundary. In this talk, we study the inviscid limit and boundary layers of some simplified NaiverStokes equations by either imposing a certain symmetry to the flow or linearizing the model around a stationary Euler flow. For the examples, we systematically use the method of correctors proposed earlier by J. L. Lions and construct an asymptotic expansion as the sum of the NavierStokes solution and the corrector. The corrector, which corrects the discrepancies between the boundary values of the viscous and inviscid solutions, is in fact an (approximating) solution of the corresponding Prandtl type equations. The validity of our asymptotic expansions is then confirmed globally in the whole domain by energy estimates on the difference of the viscous solution and the proposed expansion. This is a joint work with J. Kelliher, M. Lopes Filho, A. Mazzucato, and H. Nussenzveig Lopes.
Tau Shean Lim
Traveling Fronts of ReactionDiffusion Equations with Ignition Media and Levy Operators
We discuss traveling front solutions u(t,x) = U(xct) of reactiondiffusion equations u_t = Lu + f(u) with ignition media f and diffusion operators L generated by symmetric Levy processes X_t. Existence and uniqueness of fronts are wellknown in the case of classical diffusion (i.e., Lu = Laplacian(u)) and nonlocal diffusion (Lu = J*u  u). Our work extends these results to general Levy operators. In particular, we show that a strong diffusivity in the underlying process (in the sense that the first moment of X_1 is infinite) prevents formation of fronts, while a weak diffusivity gives rise to a unique (up to translation) front U and speed c>0.
Tarek M. ELgindi
Propagation of Singularities in Incompressible Fluids
We will discuss some recent results on the local and global stability of certain singular solutions to the incompressible 2d Euler equation. We will begin by giving a brief overview of the classical and modern results on the 2d Euler equationparticularly related to wellposedness theory in critical spaces. Then we will present a new wellposedness class which allows for merely Lipschitz continuous velocity fields and nondecaying vorticity. This will be based upon some interesting estimates for singular integrals on spaces with L^\infty scaling. After that we will introduce a class of scale invariant solutions to the 2d Euler equation and describe some of their remarkable properties including the existence of pendulumlike quasi periodic solutions and infinitetime cusp formation in vortex patches with corners. This is a joint work with I. Jeong.
Adrian Tudorascu
HamiltonJacobi equations in the Wasserstein space of probability measures
In 2008 Gangbo, Nguyen and Tudorascu showed that certain variational solutions of the EulerPoisson system in 1D can be regarded as optimal paths for the valuefunction giving the viscosity solution of some (infinitedimensional) HamiltonJacobi equation whose phasespace is the Wasserstein space of Borel probability measures with finite second moment. At around the same time, Lasry, Lions, and others became interested in such HamiltonJacobi equations (HJE) in connection with their developing theory of MeanField games. A different approach (less intrinsic than ours) to the notion of viscosity solution was preferred, one that made an immediate connection between HJE in the Wasserstein space and HJE in Hilbert spaces (whose theory was wellstudied and fairly wellunderstood). At the heart of the difference between these approaches lies the choice of the sub/supperdifferential in the context of the Wasserstein space (i.e. the interpretation of ``cotangent space to this ``pseudoRiemannian manifold) . In this talk I will start with a brief introduction to MeanField games and Optimal Transport, then I will discuss the challenges we encounter in the analysis of (our intrinsic) viscosity solutions of HJE in the Wasserstein space. Based on joint work with W. Gangbo.
Alexis Vasseur
Compressible NavierStokes equations with degenerate viscosities
We will discuss recent results on the construction of weak solutions for 3D compressible NavierStokes equations with degenerate viscosities. The method is based on the Bresch and Desjardins entropy. The main contribution is to derive MV type inequalities for the weak solutions, even if it is not verified by the first level of approximation. This provides existence of global solutions in time, for the compressible NavierStokes equations, in three dimensional space, with large initial data, possibly vanishing on the vacuum.
MinhBinh Tran
Quantum kinetic problems
After the production of the first BECs, there has been an explosion of research on the kinetic theory associated to BECs. Later, Gardinier, Zoller and collaborators derived a Master Quantum Kinetic Equation for BECs and introduced the terminology ”Quantum Kinetic Theory”. In 2012, Reichl and collaborators made a breakthrough in discovering a new collision operator, which had been missing in the previous works. My talk is devoted to the description of our recent mathematical works on quantum kinetic theory. The talk will be based on my joint works with Alonso, Gamba (existence, uniqueness, propagation of moments), Nguyen (Maxwellian lower bound), Soffer (coupling Schrodinger–kinetic equations), Escobedo (convergence to equilibrium), Craciun (the analog between the global attractor conjecture in chemical reaction network and the convergence to equilibrium of quantum kinetic equations), Reichl (derivation).
David Kaspar
Kinetics of shock clustering
Suppose we solve a (deterministic) scalar conservation law with random initial data. Can we describe the probability law of the solution as a stochastic process in x for fixed later time t? The answer is yes, for certain Markov initial data, and the probability law factorizes as a product of kernels. These kernels are obtained by solving a meanfield kinetic equation which most closely resembles the Smoluchowski coagulation equation. We discuss prior and ongoing work concerning this and related problems.
Brian Weber
DegenerateElliptic PDE and Toric Kahler 4manfiolds
Understanding scalarflat instantons is crucial for knowing how Ka ̈hler manifolds degenerate. It is known that scalarflat Kahler 4manifolds with two symmetries give rise to a pair of linear degenerateelliptic Heston type equations of the form x(fxx + fyy) + fx = 0, which were originally studied in mathematical finance. Vice versa, solving these PDE produce scalarflat Kahler 4manifolds. These PDE have been studied locally, but here we describe new global results and their implications, partic ularly a classification of scalarflat metrics on K ̈ahler 4manifolds and applications for the study of constant scalar curvature and extremal Ka ̈hler metrics.
Tianling Jin
Holder gradient estimates for parabolic homogeneous pLaplacian equations
We prove interior Holder estimates for the spatial gradient of viscosity solutions to the parabolic homogeneous pLaplacian equation u_t=\nabla u^{2p} div(\nabla u^{p2}\nabla u), where 1<p<\infty. This equation arises from tugofwar like stochastic games with white noise. It can also be considered as the parabolic pLaplacian equation in non divergence form. This is joint work with Luis Silvestre.
Russell Schwab
Neumann homogenization via integrodifferential methods
In this talk I will describe how one can use integrodifferential methods to attack some Neumann homogenization problems that is, describing the effective behavior of solutions to equations with highly oscillatory Neumann data. I will focus on the case of linear periodic equations with a singular drift, which includes (with some regularity assumptions) divergence equations with nonconormal oscillatory Neumann conditions. The analysis focuses on an induced integrodifferential homogenization problem on the boundary of the domain. This is joint work with Nestor Guillen.
Jingrui Cheng
Semigeostrophic system with variable Coriolis parameter.
The semigeostrophic system (abbreviated as SG) is a model of largescale atmospheric/ocean flows. Previous works about the SG system have been restricted to the case of constant Coriolis force, where we write the equation in "dual coordinates" and solve. This method does not apply for variable Coriolis parameter case. We develop a timestepping procedure to overcome this difficulty and prove local existence and uniqueness of smooth solutions to SG system. This is joint work with Michael Cullen and Mikhail Feldman.
Paul Rabinowitz
On A Double Well Potential System
We will discuss an elliptic system of partial differential equations of the form \[ \Delta u + V_u(x,u) = 0,\;\;x \in \Omega = \R \times \mathcal{D}\subset \R^n, \;\;\mathcal{D} \; bounded \subset \R^{n1} \] \[ \frac{\partial u}{\partial \nu} = 0 \;\;on \;\;\partial \Omega, \] with $u \in \R^m$,\; $\Omega$ a cylindrical domain in $\R^n$, and $\nu$ the outward pointing normal to $\partial \Omega$. Here $V$ is a double well potential with $V(x, a^{\pm})=0$ and $V(x,u)>0$ otherwise. When $n=1, \Omega =\R^m$ and \eqref{*} is a Hamiltonian system of ordinary differential equations. When $m=1$, it is a single PDE that arises as an AllenCahn model for phase transitions. We will discuss the existence of solutions of \eqref{*} that are heteroclinic from $a^{}$ to $a^{+}$ or homoclinic to $a^{}$, i.e. solutions that are of phase transition type.
This is joint work with Jaeyoung Byeon (KAIST) and Piero Montecchiari (Ancona).
Hong Zhang
On an elliptic equation arising from composite material
I will present some recent results on secondorder divergence type equations with piecewise constant coefficients. This problem arises in the study of composite materials with closely spaced interface boundaries, and the classical elliptic regularity theory are not applicable. In the 2D case, we show that any weak solution is piecewise smooth without the restriction of the underling domain where the equation is satisfied. This completely answers a question raised by Li and Vogelius (2000) in the 2D case. Joint work with Hongjie Dong.
Aaron Yip
Discrete and Continuous Motion by Mean Curvature in Inhomogeneous Media
The talk will describe some results on the behavior of solutions of motion by mean curvature in inhomogeneous media. Emphasis will be put on the pinning and depinning transition, continuum limit of discrete spin systems and the motion of interface between patterns.
Hiroyoshi Mitake
Selection problem for fully nonlinear equations
Recently, there was substantial progress on the selection problem on the ergodic problem for HamiltonJacobi equations, which was open during almost 30 years. In the talk, I will first show a result on the convex HamiltonJacobi equation, then tell important problems which still remain. Next, I will mainly focus on a recent joint work with H. Ishii (Waseda U.), and H. V. Tran (U. WisconsinMadison) which is about the selection problem for fully nonlinear, degenerate elliptic partial differential equations. I will present a new variational approach for this problem.
Nestor Guillen
Minmax formulas for integrodifferential equations and applications
We show under minimal assumptions that a nonlinear operator satisfying what is known as a "global comparison principle" can be represented by a minmax formula in terms of very special linear operators (Levy operators, which involve driftdiffusion and integrodifferential terms). Such type of formulas have been very useful in the theory of second order equations for instance, by allowing the representation of solutions as value functions for differential games. Applications include results on the structure of DirichlettoNeumann mappings for fully nonlinear second order elliptic equations.
Ryan Denlinger
The propagation of chaos for a rarefied gas of hard spheres in vacuum
We are interested in the rigorous mathematical justification of Boltzmann's equation starting from the deterministic evolution of manyparticle systems. O. E. Lanford was able to derive Boltzmann's equation for hard spheres, in the BoltzmannGrad scaling, on a short time interval. Improvements to the time in Lanford's theorem have so far either relied on a small data hypothesis, or have been restricted to linear regimes. We revisit the small data regime, i.e. a sufficiently dilute gas of hard spheres dispersing into vacuum; this is a regime where strong bounds are available globally in time. Subject to the existence of such bounds, we give a rigorous proof for the propagation of Boltzmann's ``onesided molecular chaos.
Misha Feldman
Shock reflection, free boundary problems and degenerate elliptic equations.
Abstract: We will discuss shock reflection problem for compressible gas dynamics, and von Neumann conjectures on transition between regular and Mach reflections. We will discuss existence of solutions of regular reflection structure for potential flow equation, and also regularity of solutions, and properties of the shock curve (free boundary). Our approach is to reduce the shock reflection problem to a free boundary problem for a nonlinear equation of mixed elliptichyperbolic type. Open problems will also be discussed, including uniqueness. The talk is based on the joint works with GuiQiang Chen, Myoungjean Bae and Wei Xiang.
Jessica Lin
Optimal Quantitative Error Estimates in Stochastic Homogenization for Elliptic Equations in Nondivergence Form
Abstract: I will present optimal quantitative error estimates in the stochastic homogenization for uniformly elliptic equations in nondivergence form. From the point of view of probability theory, stochastic homogenization is equivalent to identifying a quenched invariance principle for random walks in a balanced random environment. Under strong independence assumptions on the environment, the main argument relies on establishing an exponential version of the EfronStein inequality. As an artifact of the optimal error estimates, we obtain a regularity theory down to microscopic scale, which implies estimates on the local integrability of the invariant measure associated to the process. This talk is based on joint work with Scott Armstrong.
Sergey Bolotin
Degenerate billiards
In an ordinary billiard trajectories of a Hamiltonian system are elastically reflected when colliding with a hypersurface (scatterer). If the scatterer is a submanifold of codimension more than one, then collisions are rare. Trajectories with infinite number of collisions form a lower dimensional dynamical system. Degenerate billiards appear as limits of ordinary billiards and in celestial mechanics.
MoonJin Kang
On contraction of large perturbation of shock waves, and inviscid limit problems
This talk will start with the relative entropy method to handle the contraction of possibly large perturbations around viscous shock waves of conservation laws. In the case of viscous scalar conservation law in one space dimension, we obtain $L^2$contraction for any large perturbations of shocks up to a Lipschitz shift depending on time. Such a timedependent Lipschitz shift should be constructed from dynamics of the perturbation. In the case of multidimensional scalar conservation law, the perturbations of planar shocks are $L^2$contractive up to a more complicated shift depending on both time and space variable, which solves a parabolic equation with inhomogeneous coefficient and force terms reflecting the perturbation. As a consequence, the $L^2$contraction property implies the inviscid limit towards inviscid shock waves. At the end, we handle the contraction properties of admissible discontinuities of the hyperbolic system of conservation laws equipped with a strictly convex entropy.
Hung Tran
Some inverse problems in periodic homogenization of HamiltonJacobi equations.
Abstract: We look at the effective Hamiltonian $\overline{H}$ associated with the Hamiltonian $H(p,x)=H(p)+V(x)$ in the periodic homogenization theory. Our central goal is to understand the relation between $V$ and $\overline{H}$. We formulate some inverse problems concerning this relation. Such type of inverse problems are in general very challenging. I will discuss some interesting cases in both convex and nonconvex settings. Joint work with Songting Luo and Yifeng Yu.
Eric Baer
Optimal function spaces for continuity of the Hessian determinant as a distribution.
Abstract: In this talk we describe a new class of optimal continuity results for the action of the Hessian determinant on spaces of Besov type into the space of distributions on $\mathbb{R}^N$, obtained in collaboration with D. Jerison. Inspired by recent work of Brezis and Nguyen on the distributional Jacobian determinant, we show that the action is continuous on the Besov space $B(22/N,N)$ of fractional order, and that all continuity results in this scale of Besov spaces are consequences of this result. A key ingredient in the argument is the characterization of $B(22/N,N)$ as the space of traces of functions in the Sobolev space $W^{2,N}(\mathbb{R}^{N+2})$ on the subspace $\mathbb{R}^N$ (of codimension 2). The most elaborate part of the analysis is the construction of a counterexample to continuity in $B(22/N,p)$ with $p>N$. Tools involved in this step include the choice of suitable ``atoms" having a tensor product structure and Hessian determinant of uniform sign, formation of lacunary series of rescaled atoms, and delicate estimates of terms in the resulting multilinear expressions.
Donghyun Lee
FLUIDS WITH FREESURFACE AND VANISHING VISCOSITY LIMIT.
Abstract : Freeboundary problems of incompressible fluids have been studied for several decades. In the viscous case, it is basically solved by Stokes regularity. However, the inviscid case problem is generally much harder, because the problem is purely hyperbolic. In this talk, we approach the problem via vanishing viscosity limit, which is a central problem of fluid mechanics. To correct boundary layer behavior, conormal Sobolev space will be introduced. In the spirit of the recent work by N.Masmoudi and F.Rousset (2012, nonsurface tension), we will see how to get local regularity of incompressible freeboundary Euler, taking surface tension into account. This is joint work with Tarek Elgindi. If possible, we also talk about applying the similar technique to the freeboundary MHD(Magnetohydrodynamics). Especially, we will see that strong zero initial boundary condition is still valid for this coupled PDE. For the general boundary condition (for perfect conductor), however, the problem is still open.
HyungJu Hwang
The FokkerPlanck equation in bounded domains
abstract: In this talk, we consider the initialboundary value problem for the FokkerPlanck equation in an interval or in a bounded domain with absorbing boundary conditions. We discuss a theory of wellposedness of classical solutions for the problem as well as the exponential decay in time, hypoellipticity away from the singular set, and the Holder continuity of the solutions up to the singular set. This is a joint work with J. Jang, J. Jung, and J. Velazquez.
MinhBinh Tran
Nonlinear approximation theory for kinetic equations
Abstract: Numerical resolution methods for the Boltzmann equation plays a very important role in the practical a theoretical study of the theory of rarefied gas. The main difficulty in the approximation of the Boltzmann equation is due to the multidimensional structure of the Boltzmann collision operator. The major problem with deterministic numerical methods using to solve Boltzmann equation is that we have to truncate the domain or to impose nonphysical conditions to keep the supports of the solutions in the velocity space uniformly compact. I n this talk, we will introduce our new way to make the connection between nonlinear approximation theory and kinetic theory. Our nonlinear wavelet approximation is nontruncated and based on an adaptive spectral method associated with a new wavelet filtering technique. The approximation is proved to converge and preserve many properties of the homogeneous Boltzmann equation. The nonlinear approximation solves the equation without having to impose nonphysics conditions on the equation.
Bob Jensen
CrandallLions Viscosity Solutions of Uniformly Elliptic PDEs
Abstract: I will discuss CL viscosity solutions of uniformly elliptic partial differential equations for operators with only measurable spatial regularity. E.g., $L[u] = \sum a_{i\,j}(x)\,D_{i\,j}u(x)$ where $a_{i\,j}(x)$ is bounded, uniformly elliptic, and measurable in $x$. In general there isn't a meaningful extension of the CL viscosity solution definition to operators with measurable spatial dependence. But under uniform ellipticity there is a natural extension. Though there isn't a general comparison principle in this context, we will see that the extended definition is robust and uniquely characterizes the ``right" solutions for such problems.
Luis Silvestre
A priori estimates for integral equations and the Boltzmann equation.
Abstract: We will review some results on the regularity of general parabolic integrodifferential equations. We will see how these results can be applied in order to obtain a priori estimates for the Boltzmann equation (without cutoff) modelling the evolution of particle density in a dilute gas. We derive a bound in L^infinity for the full Boltzmann equation, and Holder continuity estimates in the space homogeneous case.
Connor Mooney
Counterexamples to Sobolev regularity for degenerate MongeAmpere equations
Abstract: W^{2,1} estimates for the MongeAmpere equation \det D^2u = f in R^n were first obtained by De Philippis and Figalli in the case that f is bounded between positive constants. Motivated by applications to the semigeostrophic equation, we consider the case that f is bounded but allowed to be zero on some set. In this case there are simple counterexamples to W^{2,1} regularity in dimension n \geq 3 that have a Lipschitz singularity. In contrast, if n = 2 a classical theorem of Alexandrov on the propagation of Lipschitz singularities shows that solutions are C^1. We will discuss a counterexample to W^{2,1} regularity in two dimensions whose second derivatives have nontrivial Cantor part, and also a related result on the propagation of Lipschitz / log(Lipschitz) singularities that is optimal by example.
Javier Gomez Serrano
Existence and regularity of rotating global solutions for active scalars
A particular kind of weak solutions for a 2D active scalar equation are the so called patches, i.e., solutions for which the scalar is a step function taking one value inside a moving region and another in the complement. The evolution of such distribution is completely determined by the evolution of the boundary, allowing the problem to be treated as a nonlocal one dimensional equation for the contour. In this talk we will discuss the existence and regularity of uniformly rotating solutions for the vortex patch and generalized surface quasigeostrophic (gSQG) patch equation. We will also outline the proof for the smooth (non patch) SQG case. Joint work with Angel Castro and Diego Cordoba.
Yifeng Yu
Gequation in the modeling of flame propagation.
Abstract: Gequation is a well known model in turbulent combustion. In this talk, I will present joint works with Jack Xin about how the effective burning velocity (turbulent flame speed) depends on the strength of the ambient fluid (e.g. the speed of the wind) under various Gequation model.
Nam Le
Global smoothness of the MongeAmpere eigenfunctions
Abstract: In this talk, I will discuss global smoothness of the eigenfunctions of the MongeAmpere operator on smooth, bounded and uniformly convex domains in all dimensions. A key ingredient in our analysis is boundary Schauder estimates for certain degenerate MongeAmpere equations. This is joint work with Ovidiu Savin.
Qin Li
Kineticfluid coupling: transition from the Boltzmann to the Euler
Abstract: Kinetic equations (the Boltzmann, the neutron transport equation etc.) are known to converge to fluid equations (the Euler, the heat equation etc.) in certain regimes, but when kinetic and fluid regime coexist, how to couple the two systems remains an open problem. The key is to understand the halfspace problem that resembles the boundary layer at the interface. In this talk, I will present a unified proof for the wellposedness of a class of halfspace equations with general incoming data, propose an efficient spectral solver, and utilize it to couple fluid with kinetics. Moreover, I will present complete error analysis for the proposed spectral solver. Numerical results will be shown to demonstrate the accuracy of the algorithm.
Lu Wang
Asymptotic Geometry of Selfshrinkers
Abstract: In this talk, we will discuss some recent progress towards the conjectural asymptotic behaviors of twodimensional selfshrinkers of mean curvature flow.
Christophe Lacave
Wellposedness for 2D Euler in nonsmooth domains
The wellposedness of the Euler system has been of course the matter of many works, but a common point in all the previous studies is that the boundary is at least $C^{1,1}$. In a first part, we will establish the existence of global weak solutions of the 2D incompressible Euler equations for a large class of nonsmooth open sets. Existence of weak solutions with $L^p$ vorticity is deduced from an approximation argument, that relates to the socalled $\gamma$convergence of domains. In a second part, we will prove the uniqueness if the open set is the interior or the exterior of a simply connected domain, where the boundary has a finite number of corners. Although the velocity blows up near these corners, we will get a similar theorem to the Yudovich's result. Theses works are in collaboration with David GerardVaret, Evelyne Miot and Chao Wang.
Jun Kitagawa (Toronto)
Regularity theory for generated Jacobian equations: from optimal transport to geometric optics
Equations of MongeAmpere type arise in numerous contexts, and solutions often exhibit very subtle qualitative and quantitative properties; this is owing to the highly nonlinear nature of the equation, and its degeneracy (in the sense of ellipticity). Motivated by an example from geometric optics, I will talk about the class of Generated Jacobian Equations; recently introduced by Trudinger, this class also encompasses, for example, optimal transport, the Minkowski problem, and the classical MongeAmpere equation. I will present a new regularity result for weak solutions of these equations, which is new even in the case of equations arising from nearfield reflector problems (of interest from a physical and practical point of view). This talk is based on joint works with N. Guillen.
Jessica Lin (Madison)
Algebraic Error Estimates for the Stochastic Homogenization of Uniformly Parabolic Equations
We establish error estimates for the stochastic homogenization of fully nonlinear uniformly parabolic equations in stationary ergodic spatiotemporal media. Based on the approach of Armstrong and Smart in the elliptic setting, we construct a quantity which captures the geometric behavior of solutions to parabolic equations. The error estimates are shown to be of algebraic order. This talk is based on joint work with Charles Smart.
Yaguang Wang (Shanghai Jiao Tong)
Stability of Threedimensional Prandtl Boundary Layers
In this talk, we shall study the stability of the Prandtl boundary layer equations in three space variables. First, we obtain a wellposedness result of the threedimensional Prandtl equations under some constraint on its flow structure. It reveals that the classical Burgers equation plays an important role in determining this type of flow with special structure, that avoids the appearance of the complicated secondary flow in the threedimensional Prandtl boundary layers. Second, we give an instability criterion for the Prandtl equations in three space variables. Both of linear and nonlinear stability are considered. This criterion shows that the monotonic shear flow is linearly stable for the three dimensional Prandtl equations if and only if the tangential velocity field direction is invariant with respect to the normal variable, which is an exact complement to the above wellposedness result for a special flow. This is a joint work with Chengjie Liu and Tong Yang.
Benoit Pausader (Princeton)
Global smooth solutions for the EulerMaxwell problem for electrons in 2 dimensions
It is well known that pure compressible fluids tend to develop shocks, even from small perturbation. We study how self consistent electromagnetic fields can stabilize these fluids. In a joint work with A. Ionescu and Y. Deng, we consider a compressible fluid of electrons in 2D, subject to its own electromagnetic field and to a field created by a uniform background of positively charged ions. We show that small smooth and irrotational perturbations of a uniform background at rest lead to solutions that remain globally smooth, in contrast with neutral fluids. This amounts to proving small data global existence for a system of quasilinear KleinGordon equations with different speeds.
Haozhao Li (University of Science and Technology of China)
Regularity scales and convergence of the Calabi flow
We define regularity scales to study the behavior of the Calabi flow. Based on estimates of the regularity scales, we obtain convergence theorems of the Calabi flow on extremal K\"ahler surfaces, under the assumption of global existence of the Calabi flow solutions. Our results partially confirm Donaldson’s conjectural picture for the Calabi flow in complex dimension 2. Similar results hold in high dimension with an extra assumption that the scalar curvature is uniformly bounded.
Jennifer Beichman (UWMadison)
Nonstandard dispersive estimates and linearized water waves
In this talk, we focus on understanding the relationship between the decay of a solution to the linearized water wave problem and its initial data. We obtain decay bounds for a class of 1D dispersive equations that includes the linearized water wave. These decay bounds display a surprising growth factor, which we show is sharp. A further exploration leads to a result relating singularities of the initial data at the origin in Fourier frequency to the regularity of the solution.
Ben Fehrman (University of Chicago)
On The Existence of an Invariant Measure for Isotropic Diffusions in Random Environments
I will discuss the existence of a unique mutually absolutely continuous invariant measure for isotropic diffusions in random environment, of dimension at least three, which are small perturbations of Brownian motion satisfying a finite range dependence. This framework was first considered in the continuous setting by Sznitman and Zeitouni and in the discrete setting by Bricmont and Kupiainen. The results of this talk should be seen as an extension of their work.
I will furthermore mention applications of this analysis to the stochastic homogenization of the related elliptic and parabolic equations with random oscillatory boundary data and, explain how the existence of an invariant measure can be used to prove a Liouville property for the environment. In the latter case, the methods were motivated by work in the discrete setting by Benjamini, DuminilCopin, Kozma and Yadin.
Vera Hur
Instabilities in nonlinear dispersive waves
I will speak on the wave breaking and the modulational instability of nonlinear wave trains in dispersive media. I will begin by a gradient blowup proof for the BoussinesqWhitham equations for water waves. I will then describe a variational approach to determine instability to long wavelength perturbations for a general class of Hamiltonian systems, allowing for nonlocal dispersion. I will discuss KdV type equations with fractional dispersion in depth. Lastly, I will explain an asymptotics approach for Whitham's equation for water waves, qualitatively reproducing the BenjaminFeir instability of Stokes waves.
SungJin Oh
Global wellposedness of the energy critical MaxwellKleinGordon equation
The massless MaxwellKleinGordon system describes the interaction between an electromagnetic field (Maxwell) and a charged massless scalar field (massless KleinGordon, or wave). In this talk, I will present a recent proof, joint with D. Tataru, of global wellposedness and scattering of this system for arbitrary finite energy data in the (4+1)dimensional Minkowski space, in which the PDE is energy critical.
Yuan Lou
Asymptotic behavior of the smallest eigenvalue of an elliptic operator and its applications to evolution of dispersal
We investigate the effects of diffusion and drift on the smallest eigenvalue of an elliptic operator with zero Neumann boundary condition. Various asymptotic behaviors of the smallest eigenvalue, as diffusion and drift rates approach zero or infinity, are derived. As an application, these qualitative results yield some insight into the evolution of dispersal in heterogeneous environments.
Diego Cordoba
Global existence solutions and geometric properties of the SQG sharp front
A particular kind of weak solutions for a 2D active scalar are the so called sharp fronts, i.e., solutions for which the scalar is a step function. The evolution of such distribution is completely determined by the evolution of the boundary, allowing the problem to be treated as a nonlocal one dimensional equation for the contour. In this setting we will present several analytical results for the surface quasigeostrophic equation (SQG): the existence of convex $C^{\infinity}$ global rotating solutions, elliptical shapes are not rotating solutions (as opposed to 2D Euler equations) and the existence of convex solutions that lose their convexity in finite time.
Greg Kuperberg
CartanHadamard and the Little Prince.
Steve Hofmann
Quantitative Rectifiability and Elliptic Equations
A classical theorem of F. and M. Riesz states that for a simply connected domain in the complex plane with a rectifiable boundary, harmonic measure and arc length measure on the boundary are mutually absolutely continuous. On the other hand, an example of C. Bishop and P. Jones shows that the latter conclusion may fail, in the absence of some sort of connectivity hypothesis. In this talk, we discuss recent developments in an ongoing program to find scaleinvariant, higher dimensional versions of the F. and M. Riesz Theorem, as well as converses. In particular, we discuss substitute results that continue to hold in the absence of any connectivity hypothesis.
Xiangwen Zhang
Alexandrov's Uniqueness Theorem for Convex Surfaces
A classical uniqueness theorem of Alexandrov says that: a closed strictly convex twice differentiable surface in R3 is uniquely determined to within a parallel translation when one gives a proper function of the principle curvatures. We will talk about a PDE proof for this thorem, by using the maximal principle and weak uniqueness continuation theorem of BersNirenberg. Moreover, a stability result related to the uniqueness problem will be mentioned. This is a joint work with P. Guan and Z. Wang. If time permits, we will also briefly introduce the idea of our recent work on Alexandrov’s theorems for codimension two submanifolds in spacetimes.
Xuwen Chen
The Rigorous Derivation of the 1D Focusing Cubic Nonlinear Schrödinger Equation from 3D Quantum Manybody Evolution
We consider the focusing 3D quantum manybody dynamic which models a dilute bose gas strongly confined in two spatial directions. We assume that the microscopic pair interaction is focusing and matches the GrossPitaevskii scaling condition. We carefully examine the effects of the fine interplay between the strength of the confining potential and the number of particles on the 3D Nbody dynamic. We overcome the difficulties generated by the attractive interaction in 3D and establish new focusing energy estimates. We study the corresponding BBGKY hierarchy which contains a diverging coefficient as the strength of the confining potential tends to infinity. We prove that the limiting structure of the density matrices counterbalances this diverging coefficient. We establish the convergence of the BBGKY sequence and hence the propagation of chaos for the focusing quantum manybody system. We derive rigorously the 1D focusing cubic NLS as the meanfield limit of this 3D focusing quantum manybody dynamic and obtain the exact 3D to 1D coupling constant.
Kyudong Choi
Finite time blow up for 1D models for the 3D Axisymmetric Euler Equations the 2D Boussinesq system
In connection with the recent proposal for possible singularity formation at the boundary for solutions of the 3d axisymmetric incompressible Euler's equations / the 2D Boussinesq system (Luo and Hou, 2013), we study models for the dynamics at the boundary and show that they exhibit a finitetime blowup from smooth data. This is joint work with T. Hou, A. Kiselev, G. Luo, V. Sverak, and Y. Yao.
Myoungjean Bae
Recent progress on study of EulerPoisson system
In this talk, I will present recent progress on the following subjects: (1) Smooth transonic flow of EulerPoisson system; (2) Transonic shock of EulerPoisson system. This talk is based on collaboration with Ben Duan, Chujing Xie and Jingjing Xiao
Philip Isett
"Hölder Continuous Euler Flows"
Motivated by the theory of hydrodynamic turbulence, L. Onsager conjectured in 1949 that solutions to the incompressible Euler equations with Holder regularity less than 1/3 may fail to conserve energy. C. De Lellis and L. Székelyhidi, Jr. have pioneered an approach to constructing such irregular flows based on an iteration scheme known as convex integration. This approach involves correcting “approximate solutions" by adding rapid oscillations which are designed to reduce the error term in solving the equation. In this talk, I will discuss an improved convex integration framework, which yields solutions with Holder regularity 1/5, as well as other related results.
Lei Wu
Geometric Correction for Diffusive Expansion in Neutron Transport Equation
We revisit the diffusive limit of a steady neutron transport equation in a 2D unit disk with onespeed velocity. The traditional method is Hilbert expansions and boundary layer analysis. We will carefully study the classical theory of the construction of boundary layers, and discuss the necessity and specific method to add the geometric correction.
Xuan Hien Nguyen
In the 1990's, Kapouleas and Traizet constructed new examples of minimal surfaces by desingularizing the intersection of existing ones, such as catenoids and planes, with Scherk surfaces. Using the same strategy, one can prove the existence of new selftranslating and selfshrinking surfaces under mean curvature flow. In this talk, we will survey the results obtained so far and propose some generalization and simplification of the techniques.
Greg Drugan (U. of Washington)
Construction of immersed selfshrinkers
Abstract: We describe a procedure for constructing immersed selfshrinking solutions to mean curvature flow. The selfshrinkers we construct have a rotational symmetry, and the construction involves a detailed study of geodesics in the upperhalf plane with a conformal metric. This is a joint work with Stephen Kleene.
Guo Luo (Caltech)
Potentially Singular Solutions of the 3D Incompressible Euler Equations
Abstract: Whether the 3D incompressible Euler equations can develop a singularity in finite time from smooth initial data is one of the most challenging problems in mathematical fluid dynamics. This work attempts to provide an affirmative answer to this longstanding open question from a numerical point of view, by presenting a class of potentially singular solutions to the Euler equations computed in axisymmetric geometries. The solutions satisfy a periodic boundary condition along the axial direction and noflow boundary condition on the solid wall. The equations are discretized in space using a hybrid 6thorder Galerkin and 6thorder finite difference method, on specially designed adaptive (moving) meshes that are dynamically adjusted to the evolving solutions. With a maximum effective resolution of over $(3 \times 10^{12})^{2}$ near the point of singularity, we are able to advance the solution up to $\tau_{2} = 0.003505$ and predict a singularity time of $t_{s} \approx 0.0035056$, while achieving a \emph{pointwise} relative error of $O(10^{4})$ in the vorticity vector $\omega$ and observing a $(3 \times 10^{8})$fold increase in the maximum vorticity $\norm{\omega}_{\infty}$. The numerical data is checked against all major blowup (nonblowup) criteria, including BealeKatoMajda, ConstantinFeffermanMajda, and DengHouYu, to confirm the validity of the singularity. A careful local analysis also suggests that the blowingup solution develops a selfsimilar structure near the point of the singularity, as the singularity time is approached.
Xiaojie Wang(Stony Brook)
Uniqueness of Ricci flow solutions on noncompact manifolds
Abstract: Ricci flow is an important evolution equation of Riemannian metrics. Since it was introduced by R. Hamilton in 1982, it has greatly changed the landscape of riemannian geometry. One of the fundamental question about ricci flow is when is its solution to initial value problem unique. On compact manifold, with arbitrary initial metric, it was confirmed by Hamilton. On noncompact manifold, we only know this is true when further restrictions are imposed to the solution. In this talk, we will discuss various conditions that guarantee the uniqueness. In particular, we will discuss in details with the following uniqueness result. Let $(M,g)$ be a complete noncompact noncollapsing $n$dimensional riemannian manifold, whose complex sectional curvature is bounded from below and scalar curvature is bounded from above. Then ricci flow with above as its initial data, on $M\times [0,\epsilon]$ for some $\epsilon>0$, has at most one solution in the class of complete riemannian metric with complex sectional curvature bounded from below.
Roman Shterenberg(UAB)
Recent progress in multidimensional periodic and almostperiodic spectral problems
Abstract: We present a review of the results in multidimensional periodic and almostperiodic spectral problems. We discuss some recent progress and old/new ideas used in the constructions. The talk is mostly based on the joint works with Yu. Karpeshina and L. Parnovski.
Antonio Ache(Princeton)
Ricci Curvature and the manifold learning problem
Abstract: In the first half of this talk we will review several notions of coarse or weak Ricci Curvature on metric measure spaces which include the works of LottVillani, Sturm and Ollivier. The discussion of the notion of coarse Ricci curvature will serve as motivation for developing a method to estimate the Ricci curvature of a an embedded submaifold of Euclidean space from a point cloud which has applications to the Manifold Learning Problem. Our method is based on combining the notion of ``Carre du Champ" introduced by BakryEmery with a result of Belkin and Niyogi which shows that it is possible to recover the rough laplacian of embedded submanifolds of the Euclidean space from point clouds. This is joint work with Micah Warren.
JeanMichel Roquejoffre (Toulouse)
Front propagation in the presence of integral diffusion
Abstract: In many reactiondiffusion equations, where diffusion is given by a second order elliptic operator, the solutions will exhibit spatial transitions whose velocity is asymptotically linear in time. The situation can be different when the diffusion is of the integral type, the most basic example being the fractional Laplacian: the velocity can be timeexponential. We will explain why, and discuss several situations where this type of fast propagation occurs.
Myoungjean Bae (POSTECH)
Free Boundary Problem related to EulerPoisson system
One dimensional analysis of EulerPoisson system shows that when incoming supersonic flow is fixed, transonic shock can be represented as a monotone function of exit pressure. From this observation, we expect wellposedness of transonic shock problem for EulerPoisson system when exit pressure is prescribed in a proper range. In this talk, I will present recent progress on transonic shock problem for EulerPoisson system, which is formulated as a free boundary problem with mixed type PDE system. This talk is based on collaboration with Ben Duan(POSTECH), Chujing Xie(SJTU) and Jingjing Xiao(CUHK).
Changhui Tan (University of Maryland)
Global classical solution and long time behavior of macroscopic flocking models
Abstract: Selforganized behaviors are very common in nature and human societies. One widely discussed example is the flocking phenomenon which describes animal groups emerging towards the same direction. Several models such as CuckerSmale and MotschTadmor are very successful in characterizing flocking behaviors. In this talk, we will discuss macroscopic representation of flocking models. These systems can be interpreted as compressible Eulerian dynamics with nonlocal alignment forcing. We show global existence of classical solutions and long time flocking behavior of the system, when initial profile satisfies a threshold condition. On the other hand, another set of initial conditions will lead to a finite time break down of the system. This is a joint work with Eitan Tadmor.
Hongjie Dong (Brown University)
Parabolic equations in timevarying domains
Abstract: I will present a recent result on the Dirichlet boundary value problem for parabolic equations in timevarying domains. The equations are in either divergence or nondivergence form with boundary blowup loworder coefficients. The domains satisfy an exterior measure condition.
Hao Jia (University of Chicago)
Long time dynamics of energy critical defocusing wave equation with radial potential in 3+1 dimensions.
Abstract: We consider the long term dynamics of radial solution to the above mentioned equation. For general potential, the equation can have a unique positive ground state and a number of excited states. One can expect that some solutions might stay for very long time near excited states before settling down to an excited state of lower energy or the ground state. Thus the detailed dynamics can be extremely complicated. However using the ``channel of energy" inequality discovered by T.Duyckaerts, C.Kenig and F.Merle, we can show for generic potential, any radial solution is asymptotically the sum of a free radiation and a steady state as time goes to infinity. This provides another example of the power of ``channel of energy" inequality and the method of profile decompositions. I will explain the basic tools in some detail. Joint work with Baoping Liu and Guixiang Xu.
Alexander Pushnitski (King's College)
An inverse spectral problem for Hankel operators
Abstract: I will discuss an inverse spectral problem for a certain class of Hankel operators. The problem appeared in the recent work by P.Gerard and S.Grellier as a step towards description of evolution in a model integrable nondispersive equation. Several features of this inverse problem make it strikingly (and somewhat mysteriously) similar to an inverse problem for SturmLiouville operators. I will describe the available results for Hankel operators, emphasizing this similarity. This is joint work with Patrick Gerard (Orsay).
Ronghua Pan (Georgia Tech)
Compressible NavierStokesFourier system with temperature dependent dissipation
Abstract: From its physical origin such as ChapmanEnskog or Sutherland, the viscosity and heat conductivity coefficients in compressible fluids depend on absolute temperature through power laws. The mathematical theory on the wellposedness and regularity on this setting is widely open. I will report some recent progress 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 NavierStokesFourier system will also be discussed. This talk is based on joint works with Junxiong Jia and Weizhe Zhang.
Myoungjean Bae (POSTECH)
Transonic shocks for EulerPoisson system and related problems
Abstract: EulerPoisson system models various physical phenomena including the propagation of electrons in submicron semiconductor devices and plasmas, and the biological transport of ions for channel proteins. I will explain difference between Euler system and EulerPoisson system and mathematical difficulties arising due to this difference. And, recent results about subsonic flow and transonic flow for EulerPoisson system will be presented. This talk is based on collaboration with Ben Duan and Chunjing Xie.
Mike Cullen (Met. Office, UK)
Modelling the uncertainty in predicting largescale atmospheric circulations
Abstract: This talk describes work on quantifying the uncertainty in climate models by using data assimilation techniques; and in estimating the properties of largescale atmospheric flows by using asymptotic limit solutions.
Mohammad Ghomi(Math. Georgia Tech)
Abstract: We show that every smooth closed curve C immersed in Euclidean 3space satisfies the sharp inequality 2(P+I)+V >5 which relates the numbers P of pairs of parallel tangent lines, I of inflections (or points of vanishing curvature), and V of vertices (or points of vanishing torsion) of C. The proof, which employs curve shortening flow with surgery, is based on corresponding inequalities for the numbers of double points, singularities, and inflections of closed curves in the real projective plane and the sphere which intersect every closed geodesic. These findings extend some classical results in curve theory including works of Moebius, Fenchel, and Segre, which is also known as Arnold's ``tennis ball theorem".
Wei Xiang (Oxford)
Abstract: The vertical shock which initially separates two piecewise constant Riemann data, passes the wedge from left to right, then shock diffraction phenomena will occur and the incident shock becomes a transonic shock. Here we study this problem on nonlinear wave system as well as on potential flow equations. The existence and the optimal regularity across sonic circle of the solutions to this problem is established. The comparison of these two systems is discussed, and some related open problems are proposed.
Adrian Tudorascu (West Virginia University)
Abstract: This chalk & board presentation will start with an interesting motivation for these systems (the simplest of which was shown to model adhesion dynamics/ballistic aggregation by Zeldovich in 1970 in a paper published in "Astronomy & Astrophysics"). A general existence result for onedimensional pressureless Euler/EulerPoisson systems with/without viscosity will be discussed. This is achieved via entropy solutions for some appropriate scalar conservation laws; I will show that these solutions encode all the information necessary to obtain solutions for the pressureless systems. I will also discuss the stability and uniqueness of solutions, which is obtained via a contraction principle in the Wasserstein metric. This is based on joint work with T. Nguyen (U. Akron).
Diego Cordoba (Madrid)
Abstract: We consider the evolution of an interface generated between two immiscible, incompressible and irrotational fluids. Specifically we study the Muskat equation (the interface between oil and water in sand) and water wave equation (interface between water and vacuum). For both equations we will study wellposedness and the existence of smooth initial data for which the smoothness of the interface breaks down in finite time. We will also discuss some open problems.
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 socalled KellerRubinsteinSternberg 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 smallscale dependent and, especially, contain undercompressive shock waves or propagating phase boundaries. Regularizationsensitive patterns often arise in continuum physics, especially in complex fluid flows. The socalled kinetic relation is introduced to characterize the correct dynamics of these nonclassical waves, and is tied to a higherorder regularization induced by a more complete model that takes into account additional smallscale physics. In the present lecture, I will especially explain the techniques of Riemann problems, Glimmtype 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 2dimensional Ricci flow. In this case we will show that ancient compact solution is either the Einstein (trivial) or one of the KingRosenau solutions.
Maria Gualdani (UT Austin)
A nonlinear diffusion model in meanfield games
We present an overview of meanfield 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 curvaturedependent motion of plane curves in a twodimensional 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 quasiperiodic 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 KenIchi Nakamura.
Ian Tice (Brown University)
Global wellposedness and decay for the viscous surface wave problem without surface tension
We study the incompressible, gravitydriven NavierStokes equations in three dimensional domains with free upper boundaries and fixed lower boundaries, in both the horizontally periodic and nonperiodic settings. The effect of surface tension is not included. We employ a novel twotier nonlinear energy method that couples the boundedness of certain highregularity norms to the algebraic decay of lowerregularity 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 wellposedness in our energy space, which yields global wellposedness 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 (NYUCourant 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 2dimensional Fano manifold which admits big [math]\alpha_{\nu, 1}[/math] or [math]\alpha_{\nu, 2}[/math] (Tian's invariants). Our method also works for 2dimensional 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 HamiltonTian conjecture in complex dimension 2.
Francois Hamel (Marseille)
Optimization of eigenvalues of nonsymmetric elliptic operators
The talk is concerned with various optimization results for the principal eigenvalues of general secondorder 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 RayleighFaberKrahn 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)
NavierStokes and Euler equations: a unified approach to the problem of blowup
The problems of blowup for NavierStokes 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 blowup problem for the equations of incompressible fluid motion. In particular, we present a new regularity criterion which is weaker than the BealeKatoMajda condition in the inviscid case, and weaker than every LadyzhenskayaProdiSerrin condition in the viscous case.
Takis Souganidis (Chicago)
Stochastic homogenization of the Gequation
The Gequation is a HamiltonJacobi equation, of levelsettype, which is used as a model in turbulent combustion. In the lecture I will present recent joint work with Pierre Cardaliaguet about the homogenization of the Gequation set in random media, when the problem is not coercive and, hence, falls outside the scope of the theory of stochastic homogenization.
Scott Armstrong (UWMadison)
Partial regularity for fully nonlinear elliptic equations
I will present some regularity results for (nonconvex) fully nonlinear equations. Such equations do not possess smooth solutions, but in joint work with Silvestre and Smart we show that the Hausdorff dimension of the singular set is less than the ambient dimension. Using an argument with a similar flavor, we prove (jointly with Silvestre) a unique continuation result for such equations.
Russell Schwab (Carnegie Mellon)
On AleksandrovBakelmanPucci type estimates for integrodifferential equations (comparison theorems with measurable ingredients)
Despite much recent (and not so recent) attention to solutions of integrodifferential equations of elliptic type, it is surprising that a fundamental result such as a comparison theorem which can deal with only measure theoretic norms of the right hand side of the equation (Ln and Linfinity) has gone unexplored. For the case of second order equations this result is known as the AleksandrovBakelmanPucci estimate (and dates back to circa 1960s), which says that for supersolutions of uniformly elliptic equation Lu=f, the supremum of u is controlled by the Ln norm of f (n being the underlying dimension of the domain). We discuss extensions of this estimate to fully nonlinear integrodifferential equations and present a recent result in this direction. (Joint with Nestor Guillen, available at arXiv:1101.0279v3 [math.AP])
Valentin Ovsienko (University of Lyon)
The pentagram map and generalized friezes of Coxeter
The pentagram map is a discrete integrable system on the moduli space of ngons in the projective plane (which is a close relative of the moduli space of genus 0 curves with n marked points). The most interesting properties of the pentagram map is its relations to the theory of cluster algebras and to the classical integrable systems (such as the Boussinesq equation). I will talk of the recent results proving the integrability as well as of the algebraic and arithmetic properties of the pentagram map. In particular, I will introduce the space of 2frieze patterns generalizing that of the classical Coxeter friezes and define the structure of cluster manifold on this space. The talk is based on joint works with Sophie MorierGenoud, Richard Schwartz and Serge Tabachnikov.
Adrian Tudorascu (West Virginia University)
Weak Lagrangian solutions for the SemiGeostrophic system in physical space
Proposed as a simplification for the Boussinesq system in a special regime, the SemiGeostrophic (SG) system is used by metereologists to model how fronts arise in large scale weather patterns. In spite of significant progress achieved in the analysis of the SG in dual space (i.e. the system obtained from the SG by a special change of variables), there are no existence results on the SG in physical space. We shall argue that weak (Eulerian) solutions for the SemiGeostrophic system in physical space exhibiting some mild regularity in time cannot yield point masses in the dual space. However, such solutions are physically relevant to the model. Thus, we shall discuss a natural generalization of Cullen & Feldman's weak Lagrangian solutions in the physical space to include the possibility of singular measures in dual space. We have proved existence of such solutions in the case of discrete measures in dual space. The talk is based on joint work with M. Feldman.
James Nolen (Duke)
Normal approximation for a random elliptic PDE
I will talk about solutions to an elliptic PDE with conductivity coefficient that varies randomly with respect to the spatial variable. It has been known for some time that homogenization may occur when the coefficients are scaled suitably. Less is known about fluctuations of the solution around its mean behavior. This talk is about the energy dissipation rate, which is a quadratic functional of the solution and a bulk property of the random material. For a finite random sample of the material, this quantity is random. In the limit of large sample size it converges to a deterministic constant. I will describe a central limit theorem: the probability law of the energy dissipation rate is very close to that of a normal random variable having the same mean and variance. I'll give an error estimate for this approximation in total variation.
Betsy Stovall (UCLA)
We will discuss recent work concerning the cubic KleinGordon equation u_{tt}  \Delta u + u \pm u^3 = 0 in two space dimensions with real valued initial data in the energy space, u(0) in H^1, u_t(0) in L^2. We show that in the defocusing case, solutions are global and have finite L^4 norm (in space and time). In the focusing case, we characterize the dichotomy between such behavior and finite time blowup for initial data having energy less than that of the ground state. In this talk, we will pay particular attention to connections with certain questions arising in harmonic analysis.
This is joint work with Rowan Killip and Monica Visan.
Charles Smart (MIT)
Optimal Lipschitz Extensions and Regularity for the Infinity Laplacian
A classical theorem of Kirszbraun states that any Lipschitz function $f : A \to \R^m$ defined on a set $A \subseteq \R^n$ can be extended to all of $\R^n$ without increasing the Lipschitz constant. The search for a canonical such extension leads one to the notion of optimal Lipschitz extension. I will discuss joint work with Evans on the regularity of optimal Lipschitz extensions in the scalar $m = 1$ case and joint work with Sheffield on the vector valued $m > 1$ case.
Yao Yao (UCLA)
Degenerate diffusion with nonlocal aggregation: behavior of solutions
The PatlakKellerSegel (PKS) equation models the collective motion of cells which are attracted by a selfemitted chemical substance. While the global wellposedness and finitetime blow up criteria are well known, the asymptotic behaviors of solutions are not completely clear. In this talk I will present some results on the asymptotic behavior of solutions when there is global existence. The key tools used in the paper are maximumprinciple type arguments as well as estimates on mass concentration of solutions. This is a joint work with Inwon Kim.
Xuan Hien Nguyen (Iowa State)
Gluing constructions for solitons and selfshrinkers under mean curvature flow
In the 1990s, Kapouleas and Traizet constructed new examples of minimal surfaces by desingularizing the intersection of existing ones with Scherk surfaces. Using this idea, one can find new examples of selftranslating solutions for the mean curvature flow asymptotic at infinity to a finite family of grim reaper cylinders in general position. Recently, it has been shown that it is possible to desingularize the intersection of a sphere and a plane to obtain a family of selfshrinkers under mean curvature flow. I will discuss the main steps and difficulties for these gluing constructions, as well as open problems.
Nestor Guillen (UCLA)
We consider the MongeKantorovich problem, which consists in transporting a given measure into another "target" measure in a way that minimizes the total cost of moving each unit of mass to its new location. When the transport cost is given by the square of the distance between two points, the optimal map is given by a convex potential which solves the MongeAmpère equation, in general, the solution is given by what is called a cconvex potential. In recent work with Jun Kitagawa, we prove local Holder estimates of optimal transport maps for more general cost functions satisfying a "synthetic" MTW condition, in particular, the proof does not really use the C^4 assumption made in all previous works. A similar result was recently obtained by Figalli, Kim and McCann using different methods and assuming strict convexity of the target.
Charles Smart (MIT)
PDE methods for the Abelian sandpile
Abstract: The Abelian sandpile growth model is a deterministic diffusion process for chips placed on the $d$dimensional integer lattice. One of the most striking features of the sandpile is that it appears to produce terminal configurations converging to a peculiar lattice. One of the most striking features of the sandpile is that it appears to produce terminal configurations converging to a peculiar fractal limit when begun from increasingly large stacks of chips at the origin. This behavior defied explanation for many years until viscosity solution theory offered a new perspective. This is joint work with Lionel Levine and Wesley Pegden.
Vlad Vicol (University of Chicago)
Title: Shape dependent maximum principles and applications
Abstract: We present a nonlinear lower bound for the fractional Laplacian, when evaluated at extrema of a function. Applications to the global wellposedness of active scalar equations arising in fluid dynamics are discussed. This is joint work with P. Constantin.
Jiahong Wu (Oklahoma State)
"The 2D Boussinesq equations with partial dissipation"
The Boussinesq equations concerned here model geophysical flows such as atmospheric fronts and ocean circulations. Mathematically the 2D Boussinesq equations serve as a lowerdimensional model of the 3D hydrodynamics equations. In fact, the 2D Boussinesq equations retain some key features of the 3D Euler and the NavierStokes equations such as the vortex stretching mechanism. The global regularity problem on the 2D Boussinesq equations with partial dissipation has attracted considerable attention in the last few years. In this talk we will summarize recent results on various cases of partial dissipation, present the work of Cao and Wu on the 2D Boussinesq equations with vertical dissipation and vertical thermal diffusion, and explain the work of Chae and Wu on the critical Boussinesq equations with a logarithmically singular velocity.
Joana Oliveira dos Santos Amorim (Universit\'e Paris Dauphine)
"A geometric look on AubryMather theory and a theorem of Birkhoff"
Given a Tonelli Hamiltonian $H:T^*M \lto \Rm$ in the cotangent bundle of a compact manifold $M$, we can study its dynamic using the Aubry and Ma\~n\'e sets defined by Mather. In this talk we will explain their importance and give a new geometric definition which allows us to understand their property of symplectic invariance. Moreover, using this geometric definition, we will show that an exact Lipchitz Lagrangian manifold isotopic to a graph which is invariant by the flow of a Tonelli Hamiltonian is itself a graph. This result, in its smooth form, was a conjecture of Birkhoff.
GuiQiang Chen (Oxford)
"Nonlinear Partial Differential Equations of Mixed Type"
Many nonlinear partial differential equations arising in mechanics and geometry naturally are of mixed hyperbolicelliptic type. The solution of some longstanding fundamental problems in these areas greatly requires a deep understanding of such nonlinear partial differential equations of mixed type. Important examples include shock reflectiondiffraction problems in fluid mechanics (the Euler equations), isometric embedding problems in in differential geometry (the GaussCodazziRicci equations), among many others. In this talk we will present natural connections of nonlinear partial differential equations with these longstanding problems and will discuss some recent developments in the analysis of these nonlinear equations through the examples with emphasis on identifying/developing mathematical approaches, ideas, and techniques to deal with the mixedtype problems. Further trends, perspectives, and open problems in this direction will also be addressed. This talk will be based mainly on the joint work correspondingly with Mikhail Feldman, Marshall Slemrod, as well as Myoungjean Bae and Dehua Wang.
Jacob GlennLevin (UT Austin)
We consider the Boussinesq equations, which may be thought of as inhomogeneous, incompressible Euler equations, where the inhomogeneous term is a scalar quantity, typically density or temperature, governed by a convectiondiffusion equation. I will discuss local and globalintime wellposedness results for the incompressible 2D Boussinesq equations, assuming the density equation has nonzero diffusion and that the initial data belongs in a Besovtype space.
Bing Wang (UW Madison)
On the regularity of limit space
This is a joint work with Gang Tian. In this talk, we will discuss how to improve regularity of the limit space by Ricci flow. We study the structure of the limit space of a sequence of almost Einstein manifolds, which are generalizations of Einstein manifolds. Roughly speaking, such manifolds are the initial manifolds of some normalized Ricci flows whose scalar curvatures are almost constants over spacetime in the L1sense, Ricci curvatures are bounded from below at the initial time. Under the noncollapsed condition, we show that the limit space of a sequence of almost Einstein manifolds has most properties which is known for the limit space of Einstein manifolds. As applications, we can apply our structure results to study the properties of K¨ahler manifolds.
Peter Polacik (University of Minnesota)
Exponential separation between positive and signchanging solutions and its applications
In linear nonautonomous secondorder parabolic equations, the exponential separation refers to the exponential decay of any signchanging solution relative to any positive solution. In this lecture, after summarizing key results on exponential separation, we show how it can be effectively used in studies of some nonlinear parabolic problems.
Kyudong Choi (UW Madison)
Estimates on fractional higher derivatives of weak solutions for the NavierStokes equations
We study weak solutions of the 3D NavierStokes equations with L^2 initial data. We prove that kth derivative of weak solutions is locally integrable in spacetime for any real k such that 1 < k < 3. Up to now, only the second derivative was known to be locally integrable by standard parabolic regularization. We also present sharp estimates of those quantities in weakL^{4/(k+1)} locally. These estimates depend only on the L^2 norm of the initial data and on the domain of integration. Moreover, they are valid even for k >= 3 as long as we have a smooth solution. The proof uses a standard approximation of NavierStokes from Leray and a blowup techniques. The local study is based on De Giorgi techniques with a new pressure decomposition. To handle the nonlocality of fractional Laplacians, Hardy space and Maximal functions are introduced. This is joint work with A. Vasseur.
Yao Yao (UW Madison)
Confinement for nonlocal interaction equation with repulsiveattractive kernels
In this talk, we consider sets of particles interacting pairwise via a potential W, which is repulsive at short distances, but attractive at long distances. The main question we consider is whether an initially compactly supported configuration remains compactly supported for all times, regardless of the number of particles. We improved the sufficient conditions on the potential W for the above confinement property to hold. This is a joint work with Jose Carrillo and Daniel Balague.
Myoungjean Bae (POSTECH)
Transonic shocks for EulerPoisson system and related problems
Abstract: EulerPoisson system models various physical phenomena including the propagation of electrons in submicron semiconductor devices and plasmas, and the biological transport of ions for channel proteins. I will explain difference between Euler system and EulerPoisson system and mathematical difficulties arising due to this difference. And, recent results about subsonic flow and transonic flow for EulerPoisson system will be presented. This talk is based on collaboration with Ben Duan and Chunjing Xie.