Stability in the homology of configuration spaces

Speaker: 

Jennifer Wilson

Institution: 

Stanford University

Time: 

Monday, November 20, 2017 - 4:00pm

Host: 

Location: 

RH 306

This talk will illustrate some topological properties of the space F_k(M) of ordered k-tuples of distinct points in a manifold M. For a fixed manifold M, as k increases, we might expect the topology of the configuration spaces F_k(M) to become increasingly complicated. Church and others showed, however, that when M is connected and open, there is a representation-theoretic sense in which these configuration spaces stabilize. In this talk I will explain these stability patterns, and describe a higher-order “secondary representation stability” phenomenon among the unstable homology classes. These results may be viewed as a representation-theoretic analogue of current work of Galatius–Kupers–Randal-Williams. The project is joint with Jeremy Miller.

Moduli spaces of critical Riemannian metrics

Speaker: 

Jeff Viaclovsky

Institution: 

University of Wisconsin, Madison

Time: 

Monday, March 6, 2017 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

A "critical" metric on a manifold is a metric which is critical for some natural geometric variational problem. Some important examples of critical metrics are Einstein metrics and extremal Kahler metrics, and such metrics typically come in families. I will discuss some aspects of the local theory of moduli spaces of critical metrics, and present some compactness results for critical metrics which say that, under certain geometric assumptions, a sequence of critical metrics has a subsequence which converges, in the Gromov-Hausdorff sense, to a singular space with orbifold singularities. I will also discuss some results regarding the reverse problem of desingularizing critical orbifolds to produce new examples of critical metrics on smooth manifolds.
 

Discovering hidden structures in complex networks

Speaker: 

Roman Vershynin

Institution: 

University of Michigan

Time: 

Wednesday, March 1, 2017 - 4:00pm to 5:00pm

Location: 

RH 306

Many real-world networks -- social, technological, biological -- have wonderful structures. Some structures may be apparent (such as trees) while others may be hidden (such as communities). How can we discover hidden structures? Known approaches to "structure mining" in networks come from a variety of disciplines, including probability,  statistics, combinatorics, physics, optimization, theoretical computer science, signal processing and information theory. We will focus on new probabilistic approaches to structure mining. They bring together insights from random matrices, random graphs and semidefinite programming.

 

This is a joint applied math and probability seminar.

Getting to Obvious

Speaker: 

Vincent Graziano

Institution: 

Case Western Reserve University

Time: 

Friday, February 24, 2017 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

I will highlight some of the methods I've previously employed in undergraduate mathematics education. These methods were drawn from the research of others and some of my own inquires. I will give insight into how the methods are brought together so that they form a cohesive whole, while fitting the needs of the both the students and the department.

Central to the discussion is a particular enlightening experience I had with one of my students.

The experience has inspired my current methods. I will discuss this my vision for further developing curriculum and more so fostering a lively dynamic atmosphere around mathematics courses, both within and without the classroom walls.

Time permitting, I'll discuss some research that is underway with regards to these approaches.
 

University Mathematics in the Digital Age

Speaker: 

Steven Heilman

Institution: 

UCLA

Time: 

Tuesday, January 10, 2017 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

We will discuss my experience and plans for teaching mathematics to students with increasing dependence on the internet. For example, we will discuss my use of online, hyperlinked lecture notes, the role of math.stackexchange.com and other websites for writing homeworks and exams, etc.  Some new course proposals will be given, including an increased role of the math department for the UCI Data Science Initiative.
 

Randomness in convection-diffusion problems

Speaker: 

Martina Hofmanova

Institution: 

Technical University Berlin

Time: 

Monday, January 30, 2017 - 3:00pm to 4:00pm

Location: 

RH 306

In this talk, I will consider quasilinear parabolic PDEs subject to stochastic or rough perturbation and explain how various assumptions on coefficients and roughness of the noise naturally ask for different notions of solution with different regularity properties and different techniques of the proofs. On the one hand, the problems under consideration will be stochastic second order parabolic PDEs with noise smooth in space, either with a possible degeneracy in the leading order operator, where only low regularity holds true, or under the uniform ellipticity assumption, where arbitrarily high regularity can be proved under suitable assumptions on the coefficients. On the other hand, I will discuss a rough pathwise approach towards these problems based on tools from paracontrolled calculus.
 

Inquiry-based techniques in a lecture classroom

Speaker: 

Victoria Akin

Institution: 

University of Chicago

Time: 

Friday, January 27, 2017 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

I will give an overview of the inquiry-based calculus course taught at the University of Chicago. I will try to highlight successes and shortcomings of the method as well as tie in current research on "flipped-type" classrooms. Finally, I will discuss methods that could possibly be incorporated in a lecture-based classroom.

Lessons from Teaching

Speaker: 

Nguyen Nguyen

Institution: 

Northwestern University

Time: 

Thursday, January 26, 2017 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

Teaching is a learning process, with both ups and downs. In this talk, I will discuss some of the trends I have observed as I progressed from being a student to being an instructor. These include the effects of technology on Mathematics education, approaches to teaching Mathematics, etc. I will also discuss some of the lessons I have learned along the way.

Random discrete structures: Phase transitions, scaling limits, and universality

Speaker: 

Sanchayan Sen

Institution: 

McGill University

Time: 

Monday, January 23, 2017 - 4:00pm to 5:00pm

Location: 

RH 306
 
The aim of this talk is to give an overview of some recent results in two interconnected areas:
 
a) Random graphs and complex networks: The last decade of the 20th century saw significant growth in the availability of empirical data on networks, and their relevance in our daily lives. This stimulated activity in a multitude of fields to formulate and study models of network formation and dynamic processes on networks to understand real-world systems.
 
One major conjecture in probabilistic combinatorics, formulated by statistical physicists using non-rigorous arguments and enormous simulations in the early 2000s, is as follows: for a wide array of random graph models on n vertices and degree exponent \tau>3, typical distance both within maximal components in the critical regime as well as on the minimal spanning tree on the giant component in the supercritical regime scale like n^{\frac{\tau\wedge 4 -3}{\tau\wedge 4 -1}}. In other words, the degree exponent determines the universality class the random graph belongs to. The mathematical machinery available at the time was insufficient for providing a rigorous justification of this conjecture.
 
More generally, recent research has provided strong evidence to believe that several objects, including 
(i) components under critical percolation,
(ii) the vacant set left by a random walk, and
(iii) the minimal spanning tree,
constructed on a wide class of random discrete structures converge, when viewed as metric measure spaces, to some random fractals in the Gromov-Hausdorff-Prokhorov sense, and these limiting objects are universal under some general assumptions. We report on recent progress in proving these conjectures.
 
b) Stochastic geometry:  In contrast, less precise results are known in the case of spatial systems. We discuss a recent result concerning the length of spatial minimal spanning trees that answers a question raised by Kesten and Lee in the 90's, the proof of which relies on a variation of Stein's method and a quantification of the classical Burton-Keane argument in percolation theory.
 
Based on joint work with Louigi Addario-Berry, Shankar Bhamidi, Nicolas Broutin, Sourav Chatterjee, Remco van der Hofstad, and Xuan Wang.

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