Organizers: Niranjan Ramachandran, Dio Margetis, and Leo Koralov
When:
Wednesday @ 3:15pm, Tea 2:45pm - 3:15 pm in room 3201
Where:
Math 3206
From time to time special colloquia are held on other days, sometimes as part of conferences.
Other special colloquia are the Aziz Lectures and Avron Douglis Memorial Lectures.

Archives: 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018

• Speaker: () -

When: Wed, September 13, 2017 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Samir Khuller (University of Maryland Computer Science ) - https://www.cs.umd.edu/users/samir/

When: Wed, September 20, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: NP-complete problems abound in every aspect of our daily lives. One approach is to simply deploy heuristics, but for many of these we do not have any idea as to when the heuristic is effective and when it is not. Approximation algorithms have played a major role in the last three decades in developing a foundation for a better understanding of optimization techniques - greedy algorithms, algorithms based on LinearProgramming (LP) relaxations have paved the way for the design of (in some cases) optimal heuristics. Are these the best ones to use in âtypicalâ instances? Maybe, maybe not.

In this talk we will focus on two specific areas - one is in the use of greedy algorithms for a basic graph problem called connected dominating set, and the other is in the development of LP based algorithms for a basic scheduling problem in the context of data center scheduling.
• Speaker: (CMNS Dean's Office) -

When: Wed, September 27, 2017 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Vladimir Matveev (Friedrich-Schiller-UniversitÃ¤t Jena ) - http://users.minet.uni-jena.de/~matveev/

When: Wed, October 4, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: We introduce a construction that associates a Riemannian metric $g_F$ (called the
Binet-Legendre metric) to a
given Finsler metric $F$ on a smooth manifold $M$. The transformation
$F \mapsto g_F$ is $C^0$-stable and has good
smoothness properties, in contrast to previously considered
constructions. The Riemannian metric $g_F$ also behaves nicely under
conformal or isometric transformations of the Finsler metric $F$ that
makes it a powerful tool in Finsler geometry. We illustrate that by
solving a number of named problems in Finsler geometry. In particular
we extend a classical result of Wang to all dimensions. We answer a
question of Matsumoto about local conformal mapping between two
Berwaldian spaces and use it to investigation of essentially conformally Berwaldian manifolds.
We describe all possible conformal self maps and all self similarities
on a Finsler manifold, generasing the famous result of Obata to Finslerian manifolds. We also classify all compact conformally flat
Finsler manifolds. We solve a conjecture of Deng and Hou on locally
symmetric Finsler spaces. We prove smoothness of isometries of Holder-continuous Finsler metrics. We construct new easy to calculate''
conformal and metric invariants of finsler manifolds.
The results are based on the papers arXiv:1104.1647, arXiv:1409.5611,
arXiv:1408.6401, arXiv:1506.08935,
arXiv:1406.2924
partially joint with M. Troyanov (EPF Lausanne) and Yu. Nikolayevsky (Melbourne).
• Speaker: General Departmental Meeting () -

When: Wed, October 11, 2017 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Departmental Meeting () -

When: Wed, October 18, 2017 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Departmental Meeting () -

When: Wed, October 25, 2017 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Xuhua He (UMD) - http://www.math.umd.edu/~xuhuahe/

When: Wed, November 1, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: In Linear Algebra 101, we encounter two important features of the group of invertible matrices: Gauss elimination method, or the LU decomposition of almost all matrices, which is an important special case of the Bruhat decomposition; the Jordan normal form, which gives a classification of the conjugacy classes of invertible matrices.

The study of the interaction between the Bruhat decomposition and the conjugation action is an important and very active area. In this talk, we focus on the affine Deligne-Lusztig variety, which describes the interaction between the Bruhat decomposition and the Frobenius-twisted conjugation action of loop groups. The affine Deligne-Lusztig variety was introduced by Rapoport around 20 years ago and it has found many applications in arithmetic geometry and number theory.

In this talk, we will discuss some recent progress on the study of affine Deligne-Lusztig varieties, and some applications to Shimura varieties.
• Speaker: Pierre-Emmanuel Jabin (UMD) - http://www2.cscamm.umd.edu/~jabin/

When: Wed, November 8, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: We present a new method to derive quantitative estimates proving the propagation of chaos for large stochastic or deterministic systems of interacting particles. Our approach requires to prove large deviations estimates for non-continuous potentials modified by the limiting law. But it leads to explicit bounds on the relative entropy between the joint law of the particles and the tensorized law at the limit; and it can be applied to very singular kernels that are only in negative Sobolev spaces and include the Biot-Savart law for 2d Navier-Stokes
• Speaker: Simon Levin (Princeton ) -

When: Wed, November 15, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: One of the deepest problems in ecology is in understanding how so many species coexist, competing for a limited number of resources. This motivated much of Darwinâs thinking, and has remained a theme explored by such key thinkers as Hutchinson (âThe paradox of the planktonâ), MacArthur, May and others. A key to coexistence, is in the development of spatial and spatio-temporal patterns, and in the coevolution of life-history patterns that both generate and exploit spatio-temporal heterogeneity. Here, general theories of pattern formation, which have been prevalent not only in ecology but also throughout science, play a fundamental role in generating understanding. The interaction between diffusive instabilities, multiple stable basins of attraction, critical transitions, stochasticity and far-from-equilibrium phenomena creates a broad panoply of mechanisms that can contribute to coexistence, as well as a rich set of mathematical questions and phenomena. This lecture will cover as much of this as time allows.
• Speaker: () -

When: Fri, November 17, 2017 - 3:00pm
Where: Kirwan Hall 3206

View Abstract

Abstract: Our lecturers Hilaf Hasson, Kendall Williams and Allan Yashinski will be hosting the panel on the realities of teaching. The target audience first includes Math TAs but we are hoping to attract many in the department. Light refreshments to follow in room 3201.

When: Wed, November 29, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: Parabolic dynamical systems are systems of intermediate (polynomial) orbit growth. Most important classes of parabolic systems are: unipotent flows on homogeneous spaces and their smooth time changes, smooth flows on compact surfaces, translation flows and IET's (interval exchange transformations). Since the entropy of parabolic systems is zero, other properties describing chaoticity are crucial: mixing, higher order mixing, decay of correlations.
One of the most important tools in parabolic dynamics is the Ratner property (on parabolic divergence), introduced by M. Ratner in the class of horocycle flows. This property was crucial in proving famous Ratner's rigidity theorems in the above class.

We will introduce generalisations of Ratner's property for other parabolic systems and discuss it's consequences for chaotic properties. In particular this allows to approach the Rokhlin problem in the class of smooth flows on surfaces and in the class of smooth time changes of Heisenberg nilflows.
• Speaker: Zhiren Wang

When: Wed, December 6, 2017 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: Sarnak's Mobius disjointness conjecture speculates that the Mobius sequence is disjoint to all topological dynamical systems of zero topological entropy. We will survey the recent developments in this area, and discuss several special classes of dynamical systems of controlled complexity that satisfy this conjecture. Part of the talk is based on joint works with Wen Huang, Xiangdong Ye, and Guohua Zhang. No background knowledge in either dynamical systems or number theory will be assumed.

• Speaker: David Simmons (University of York) -

When: Thu, December 7, 2017 - 2:00pm
Where: Kirwan Hall 3206

View Abstract

Abstract: Abstract: In this talk, I will discuss a long-standing open problem in the dimension theory of dynamical systems, namely whether every expanding repeller has an ergodic invariant measure of full Hausdorff dimension, as well as my recent result showing that the answer is negative. The counterexample is a self-affine sponge in $\mathbb R^3$ coming from an affine iterated function system whose coordinate subspace projections satisfy the strong separation condition. Its dynamical dimension, i.e. the supremum of the Hausdorff dimensions of its invariant measures, is strictly less than its Hausdorff dimension. More generally we compute the Hausdorff and dynamical dimensions of a large class of self-affine sponges, a problem that previous techniques could only solve in two dimensions. The Hausdorff and dynamical dimensions depend continuously on the iterated function system defining the sponge, which implies that sponges with a dimension gap represent a nonempty open subset of the parameter space. This work is joint with Tushar Das (Wisconsin -- La Crosse).
• Speaker: Daniel Tataru (UC Berkeley) - https://math.berkeley.edu/~tataru/

When: Fri, December 8, 2017 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Alfio Quarteroni (Politecnico di Milano, Milan, Italy and EPFL, Lausanne, Switzerland ) - https://cmcs.epfl.ch/people/quarteroni

When: Fri, February 2, 2018 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: Abstract : In this presentation I will highlight the great potential offered by the interplay between data science and computational science to efficiently solve real life large scale problems . The leading application that I will address is the numerical simulation of the heart function.

The motivation behind this interest is that cardiovascular diseases unfortunately represent one of the leading causes of death in Western Countries.

Mathematical models based on first principles allow the description of the blood motion in the human circulatory system, as well as the interaction between electrical, mechanical and fluid-dynamical processes occurring in the heart. This is a classical environment where multi-physics processes have to be addressed.

Appropriate numerical strategies can be devised to allow for an effective description of the fluid in large and medium size arteries, the analysis of physiological and pathological conditions, and the simulation, control and shape optimization of assisted devices or surgical prostheses.

This presentation will address some of these issues and a few representative applications of clinical interest.
• Speaker: Claude Le Bris () -

When: Wed, February 7, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Weiqiang Wang (University of Virginia) - http://math.virginia.edu/people/ww9c/

When: Wed, February 14, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Ivan Cheltsov (University of Edinburgh, UK) - http://www.maths.ed.ac.uk/cheltsov/

When: Wed, February 21, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Richard Schwartz (Brown University) - http://www.math.brown.edu/~res/

When: Wed, March 14, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Richard Montgomery (UCSC) - https://people.ucsc.edu/~rmont/

When: Wed, March 28, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Shrawan Kumar (UNC at Chapel Hill) - http://www.unc.edu/math/Faculty/kumar/

When: Wed, April 18, 2018 - 3:15pm
Where: Kirwan Hall 3206

View Abstract

Abstract: TBA

When: Wed, April 25, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: TBA Kirwan Lecture () -

When: Fri, April 27, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Lillian Pierce (Duke University/IAS) - https://services.math.duke.edu/~pierce/

When: Wed, May 2, 2018 - 3:15pm
Where: Kirwan Hall 3206
• Speaker: Arnaud Debussche (ENS, Rennes, France) - http://w3.ens-rennes.fr/math/people/arnaud.debussche/

When: Fri, May 4, 2018 - 3:15pm
Where: Kirwan Hall 3206