Some quantitative Sobolev estimates for planar infinity harmonic functions

Speaker: 

Yi Zhang

Institution: 

Mathematical Institute of the University of Bonn

Time: 

Tuesday, January 16, 2018 - 3:00pm

Host: 

Location: 

RH306

Given a planar infinity harmonic function u, for each
$\alpha>0$ we show a quantitative $W^{1,\,2}_{\loc}$-estimate of
$|Du|^{\alpha}$, which is sharp when $\alpha\to 0$.  As a consequence we
obtain an $L^p$-Liouville property for infinity harmonic functions in
the whole plane
 

Neoclassical Theory of Electromagnetic Interactions

Speaker: 

Alexander Figotin

Institution: 

UC Irvine

Time: 

Friday, January 26, 2018 - 4:00pm

Location: 

MSTB 120

The theory of electromagnetic (EM) phenomena known as electrodynamics is one of the major theories in science. At macroscopic scales the interaction of the EM field with matter is described by the classical electrodynamics based on the Maxwell-Lorentz theory. Many of electromagnetic phenomena at microscopic scales are covered by the so-called semiclassical theory that treats the matter according to the quantum mechanics, whereas the EM field is treated classically. The subject of this presentation is a recently advanced by us neoclassical electromagnetic theory that describes EM phenomena at all spatial scales –microscopic and macroscopic. This theory modifies the classical electrodynamics into a theory that applies to all spatial scales including atomic and nanoscales. The neoclassical theory is conceived as one theory for all spatial scales in which the classical and quantum aspects are naturally unified and emerge as approximations. It is a classical Lagrangian field theory, and consequently it is a local and deterministic theory. Probabilistic aspects of the theory may arise in it effectively through complex nonlinear dynamical evolution. This presentation is to provide an introduction to our theory including a concise historical review.

(Joint work with Anatoli Babin)

Lowest Order Piecewise Polynomial Approximation of H^m Functions in ℝ^n

Speaker: 

Jinchao Xu

Institution: 

The Pennsylvania State University

Time: 

Friday, February 2, 2018 - 4:00pm to 5:00pm

Host: 

Location: 

RH306

In this talk, we report a recent joint work with Shuonan Wu that gives a universal construction of simplicial finite element methods for 2m-th order partial differential equations in  ℝ^n, for any m≥1, n≥1. This family of finite element space consists of piecewise polynomials of degree not greater than m.  It has some natural inclusion properties as in the corresponding Sobolev spaces in the continuous cases and it recovers the MWX element when n≥m.  We establish quasi-optimal error estimates in an appropriate energy norm. The theoretical results are further validated by numerical tests.

Dynamical properties of multiplicative functions.

Speaker: 

Oleksiy Klurman

Institution: 

Royal Institute of Technology

Time: 

Thursday, February 8, 2018 - 3:00pm to 4:00pm

Understanding joint behaviour of $(f(n),g(n+1))$ where f and g are given multiplicative functions play key role in analytic number theory with potentially profound consequences such as Riemann hypothesis, twin prime conjecture, Chowla's conjecture and many others.

In the the first part of this talk, I will discuss joint work with A. Mangerel, answering an old question of Katai about distribution of points $\{(f(n),g(n+1))\}_{n\ge 1}\in \mathbb{T}^2,$ where f and g are unimodular multiplicative functions.  

In the second part of the talk, which is based on a joint work with P. Kurlberg, answering a question of M. Lemanczyk, we construct deterministic example of multiplicative function $f:{\mathbb{N}\to \{+1,-1\}$ with various ergodic properties with respect to the Mirsky measure and discuss its relation to the interplay between Chowla conjecture and Riemann hypothesis. 

 

 

Min-max theory for constant mean curvature hypersurfaces

Speaker: 

Jonathan Zhu

Institution: 

Harvard University

Time: 

Tuesday, January 16, 2018 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

We describe the construction of closed constant mean curvature (CMC) hypersurfaces using min-max methods. In particular, our theory allows us to show the existence of closed CMC hypersurfaces of any prescribed mean curvature in any closed Riemannian manifold. This work is joint with Xin Zhou.

Bi-free probability and an approach to conjugate variables

Speaker: 

Ian Charlesworth

Institution: 

UCSD

Time: 

Tuesday, February 27, 2018 - 11:00am

Location: 

RH 306

Free entropy theory is an analogue of information theory in a non-commutative setting, which has had great applications to the examination of structural properties of von Neumann algebras. I will discuss some ongoing joint work with Paul Skoufranis to extend this approach to the setting of bi-free probability which attempts to study simultaneously ``left'' and ``right'' non-commutative variables. I will speak in particular of an approach to a bi-free Fisher information and bi-free conjugate variables -- analogues of Fisher's information measure and the score function of information theory. The focus will be on constructing these tools in the non-commutative setting, and time permitting, I will also mention some results such as bi-free Cramer-Rao and Stam inequalities, and some quirks of the bi-free setting which are not present in the free setting.

Magnetic vortex lattices

Speaker: 

Israel Michael Sigal

Institution: 

University of Toronto

Time: 

Monday, January 8, 2018 - 2:00pm

Host: 

Location: 

RH 340N

 The Ginzburg - Landau equations play a fundamental role in various areas of physics, from  superconductivity to elementary particles. They present the natural and simplest extension of the Laplace equation to line bundles. Their non-abelian generalizations - Yang-Mills-Higgs and Seiberg-Witten equations have applications in geometry and topology. 

      Of a special interest are the least energy (per unit volume) solutions of the Ginzburg - Landau equations. These turned out to have a beautiful structure of (magnetic) vortex lattices discovered by A.A. Abrikosov. (Their discovery was recognized a Nobel prize. Finite energy excitations are magnetic vortices, called Nielsen-Olesen or Nambu strings, in the particle physics.)

      I will review recent results about the vortex lattice solutions and their relation to the energy minimizing solutions on Riemann surfaces and, if time permits, to the microscopic (BCS) theory.

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