Teaching large scale optimization at the undergraduate level

Speaker: 

Daniel O'Connor

Institution: 

UCLA

Time: 

Friday, January 19, 2018 - 3:00pm to 4:00pm

Location: 

RH 306

Proximal algorithms offer state of the art performance for many large scale optimization problems. In recent years, the proximal algorithms landscape has simplified, making the subject quite accessible to undergraduate students. Students are empowered to achieve impressive results in areas such as image and signal processing, medical imaging, and machine learning using just a page or two of Python code. In this talk I'll discuss my experiences teaching proximal algorithms to students in the Physics and Biology in Medicine program at UCLA. I'll also share some of my teaching philosophy and approaches to teaching undergraduate math courses. Finally, I'll discuss my own research in optimization algorithms for radiation treatment planning, which is a fruitful source of undergraduate research projects.
 

Efficient algorithms for phase retrieval in high dimensions

Speaker: 

Yan Shuo Tan

Institution: 

University of Michigan

Time: 

Thursday, February 8, 2018 - 11:00am to 12:00pm

Host: 

Location: 

RH 306P

Mathematical phase retrieval is the problem of solving systems of rank-1 quadratic equations. Over the last few years, there has been much interest in constructing algorithms with provable guarantees. Both theoretically and empirically, the most successful approaches have involved direct optimization of non-convex loss functions. In the first half of this talk, we will discuss how stochastic gradient descent for one of these loss functions provably results in (rapid) linear convergence with high probability. In the second half of the talk, we will discuss a semidefinite programming algorithm that simultaneously makes use of a sparsity prior on the solution vector, while overcoming possible model misspecification.

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.

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