# MSCS Seminar Calendar

Saturday February 28, 2015

**Midwest Topology Seminar**

An algebraic model for commutative HZ-algebras

Birgit Richter (Universität Hamburg)

10:00 AM in Lecture Center F, Room 4

This is a report on joint work with Brooke Shipley. We show that there is a chain of Quillen equivalences between the model categories of commutative HZ-algebra spectra and $E_\infty$-monoids in unbounded chain complexes. We also provide a Quillen equivalence with commutative I-chain complexes where I is the category of finite sets and injective maps. I'll explain the equivalences and, if time permits, discuss some examples.

**Midwest Topology Seminar**

Some strange phenomena in the motivic stable homotopy groups

Dan Isaksen (Wayne State University)

11:30 AM in Lecture Center F, Room 4

I will describe some recent discoveries concerning motivic stable homotopy groups over C and over R. These include some surprises, which suggest that motivic stable homotopy groups are less like their classical counterparts than we had anticipated. Some examples are:
1) new families of non-nilpotent elements.
2) periodicities other than v_n-periodicity.
3) non-classical values for the image of J.
Parts of this talk overlap with work of Michael Andrews, Dan Dugger, Bogdan Gheorghe, Bert Guillou, and Zhouli Xu.

**Midwest Topology Seminar**

Tmf_0(3)

Lennart Meier (University of Virginia)

2:30 PM in Lecture Center F, Room 4

Quite recently, Mike Hill and Tyler Lawson defined "compactified" versions of topological modular forms with level structures. The goal of this talk is to explore these new versions in the example of Tmf_0(3). In particular, we will compute its Picard group and its Anderson dual. Throughout, ideas from equivariant homotopy theory will be important, especially the use of representation spheres.

**Midwest Topology Seminar**

The ring cooperations for 2-primary tmf

Mark Behrens (University of Notre Dame)

4:00 PM in Lecture Center F, Room 4

This talk represents joint work with Kyle Ormsby, Nat Stapleton, and
Vesna Stojanoska. I will describe 3 different perspective on tmf_*tmf
(localized at 2). (1) the E_2-term of the Adams spectral sequence for
tmf ^ tmf decomposes as a direct sum of ext groups associated to
bo-Brown-Gilter modules, (2) modulo torsion, tmf_*tmf embeds into the
ring of 2-variable modular forms, and (3) modulo v_2-torsion, tmf_*tmf
embeds into a product of TMF_0(N)_*, for various values of N, and how
they are related.

Monday March 2, 2015

**Geometry, Topology and Dynamics Seminar**

Functoriality in mirror symmetry

Mohammed Abouzaid (Columbia University)

3:00 PM in SEO 636

After discussing the basic ideas behind mirror symmetry and
Floer theory, I will discuss how to relate mirror symmetry for a
variety to mirror symmetry for a divisor, and to its complement.
This is a report on joint work with Paul Seidel and Sheel Ganatra.

**Combinatorics Seminar**

Some new results on random points in the unit square

Alan Frieze (Carnegie Mellon)

3:00 PM in SEO 427

Suppose that X1,X2,...Xn are chosen randomly from the unit
square. (More generally from the unit cube in d dimensions).
We consider the following:
Paper 1: Travelling in randomly embedded random graphs.
1. If the points are joined by an edge with probability p, what can one
say about the shortest path distance in this embedding of G(n.p) as
compared to the Euclidean distance.
2. To what extent can the Beardwood, Halton, Hammersley theorem on the
length of the shortest TSP tour be extended to this case?
Paper 2: Separating subadditive Euclidean functionals.
For many optimization problems we know that a.s. growth rate of the
optimum value up to a constant, e.g. for TSP, Minimum Spanning Tree,
Steiner Tree, Perfect Matching, 2-factor. We know that a.s. these
optimum values are all within a constant factor of each other, but we do
not in general know the constants and so the question arises as to
whether different problems give rise to different constants. We prove
that these constants are indeed different and give a negative
computational consequence in respect of using the 2-factor approximation
for solving the TSP via branch and bound.
Joint work with Wes. Pegden.

**Graduate Theoretical Computer Science Seminar**

Hardness amplification using error correcting codes

Jeremy Kun (UIC)

4:00 PM in SEO 427

We'll discuss the applications of efficient local decoding techniques to amplify a worst-case hard function for circuits to an average-case hard function. Together with a previous talk by Adam Lelkes on the Nisan-Wigderson pseudoranom generator, this gives a complete derandomization of BPP from the existence of a worst-case hard function.

**Applied Mathematics Seminar**

Numerical simulations of the primitive equations with humidity and saturations above mountain

Youngjoon Hong (Indiana University Bloomington)

4:00 PM in SEO 636

New avenues are explored to study the two dimensional inviscid primitive equations of the atmosphere with humidity and saturation, in presence of topography and subject to physically plausible boundary conditions for the system of equations. The filtering of the gravity waves produces a compatibility condition similar to the condition of incompressibility for the Navier-Stokes equations, which we treat in a similar manner. In that respect, a version of the projection method is introduced to enforce the compatibility condition on the horizontal velocity field, which comes from the boundary conditions. The resulting scheme allows for a significant reduction of the errors near the topography when compared to more standard finite volume schemes.

Tuesday March 3, 2015

**Logic Seminar**

The model-theoretic content of a result of Junge and Pisier

Isaac Goldbring (UIC)

4:00 PM in SEO 427

An operator space is a norm closed linear subspace of the Banach space B(H) of bounded linear operators on a Hilbert space. For reasons that will be explained in this talk, operator spaces are the noncommutative analogs of Banach spaces. A fundamental result of Junge and Pisier shows that there are many more operator spaces than there are Banach spaces in a way to be made precise in the talk. I will explain the model-theoretic content of their result. Parts of this talk represent joint work with Martino Lupini and other parts represent joint work with Thomas Sinclair.

Wednesday March 4, 2015

**Geometry, Topology and Dynamics Seminar**

Minimal self joinings of 3-IETs

Kelly Yancey (University of Maryland)

3:00 PM in SEO 612

In this talk we will discuss substitution systems that have the property of minimal self joining. Then we will focus our attention on self-similar interval exchange transformations and their associated substitutions. We will show that
3-IETs have MSJ. This is joint with Giovanni Forni.

**Statistics Seminar**

Model-free variable selection via learning gradients

Lei Yang (UIC)

4:00 PM in SEO 636

Variable selection is popular in high-dimensional data analysis to identify the truly informative variables. Many variable selection methods have been developed under various model assumptions, such as linear model and additive model. However, their success largely rely on validity of the assumed models. In this talk, I will introduce a model-free variable selection method based on gradient learning. The key idea is that if a variable is informative is equivalent to if its corresponding gradient function is substantially non-zero. The proposed method is formulated in a framework of learning gradients equipped with a flexible reproducing kernel Hilbert space. Computationally, a blockwise majorization decent (BMD) algorithm is introduced for efficient computation. Theoretically, without assuming explicit models, the estimation and variable selection consistencies are established. A variety of simulated examples and real-life examples are provided to evaluate the performance.

Monday March 9, 2015

**Geometry, Topology and Dynamics Seminar**

A Lagrangian Floer theory in the pillowcase and traceless representations of tangles.

Paul Kirk (Indiana University)

3:00 PM in SEO 636

I’ll describe a construction of a Z/4 graded Lagrangian-Floer theory for immersed curves in the pillowcase ($T^2/(Z/2)$) and apply it to character varieties of traceless representations of tangles in 3-manifolds. I’ll illustrate with examples and speculate about its connection to Kronheimer-Mrowka’s singular intanton knot floer homology.

Tuesday March 10, 2015

**Logic Seminar**

Tight embeddability of metric spaces

Florent Baudier (Texas A&M)

4:00 PM in SEO 427

We introduce the notion of almost Lipschitz embeddability and study the almost Lipschitz embeddability of proper metric
spaces into Banach spaces. We will discuss the relevance of our work in topology and geometric group theory.
We intend to open the seminar with a brief review (which should be accessible to non-specialists) of some interesting aspects of metric embedding theory.

**Mathematics Education Colloquium**

Mathematical Goals, Formative Assessment, and Textbooks: Challenges, connections and implications for practice

Valerie Mills (President of the National Council of Supervisors of Mathematics)

5:00 PM in SEO 636

Abstract: Research on the use of formative assessment suggests that it has the potential to lift student achievement in classrooms and across school systems. During this session participants will explore some of the hidden inherent challenges that problematize the use of formative assessment for teachers as well as promising shifts in practice that can support more effective use of formative assessment strategies.

Wednesday March 11, 2015

**Special Colloquium**

Geometry of Space, Physics and Analysis

Shing-Tung Yau (Harvard)

4:00 PM in BSB 250

The concept of space has gone through many stages of evolutions. Many of them are related to the advancement of our understanding of the nature: from Euclidean geometry to analytic geometry and calculus; from intrinsic Gauss curvature to Riemannian geometry and to Einstein's general relativity; from conformal geometry to complex manifolds and to string theory; from fiber bundles to gauge theory and to quantum field
theory... These developments display a beautiful blend of geometry, analysis and physics, with the goal of unifying all the forces in nature.

Shing-Tung Yau, one of the most celebrated and influential mathematicians of our times, is the Graustein Professor of Mathematics at Harvard. He received a Ph.D from University of California, Berkeley at the age of 22. He was awarded the Fields Medal, the Crafoord Prize, the Wolf Prize and the National Medal of Science. He is the founder and leading figure of geometric analysis and solved the Calabi conjecture in algebraic geometry and positive mass conjecture in general relativity which have had a profound influence on a wide range of scientific disciplines.
There will be a reception after the talk.

Friday March 13, 2015

Monday March 16, 2015

Tuesday March 17, 2015

Wednesday March 18, 2015

**Statistics Seminar**

A new nonparametric stationarity test of time series in time domain

Professoe Suojin Wang (Texas A & M University)

4:00 PM in SEO 636

In this talk, we present a new double order selection test for checking second-order stationarity of a time series. To develop the test, a sequence of systematic samples are defined via the Walsh functions. Then the deviations of the autocovariances based on these systematic samples from the corresponding autocovariances of the whole time series are calculated and the uniform asymptotic joint normality of these deviations over different systematic samples is obtained. With a double order selection scheme, our test statistic is constructed by combining the deviations at different lags in the systematic samples. The null asymptotic distribution of the proposed statistic is derived and the consistency of the test is shown under fixed and local alternatives. Simulation studies demonstrate well-behaved finite sample properties of the proposed method. Comparisons with some existing tests in terms of power are given both analytically and empirically. In addition, the proposed method is applied to check the stationarity assumption of a chemical process viscosity readings data.

Friday March 20, 2015

Monday March 30, 2015

Wednesday April 1, 2015

Friday April 3, 2015

Monday April 6, 2015

**Geometry, Topology and Dynamics Seminar**

Morse geodesics in torsion groups

Elisabeth Fink (Ecole Normale Superieure)

3:00 PM in SEO 636

A geodesic in a metric space is Morse, if quasi-geodesics connecting points on it stay uniformly close. In many cases, such geodesics come from an embedded cyclic subgroup, in other words from a so-called Morse element which generates this cyclic subgroup. By studying asymptotic cones, we will exhibit Morse geodesics in infinite torsion groups which are direct limits of hyperbolic groups. On the contrary, it will be shown that there exist many non-Morse geodesics in the same groups, which do not even contain arbitrarily large powers. I will also discuss related properties and possible consequences.

Wednesday April 8, 2015

Friday April 10, 2015

**Departmental Colloquium**

Interpolation for polynomials in several variables

Joe Harris (Harvard)

3:00 PM in SEO 636

An elementary theorem says that we can always find a polynomial $f(x)$ of degree $d$ or less having specified values at $d+1$ given points $x$. When we try to state (let alone prove) an analogue for polynomials in several variables, however, we run into immediate difficulties. In this talk, I’ll try to show that the difficulties lie in the geometry of the points, and suggest at least a conjectural answer to the problem.

Opening lecture: Midwest Algebraic Geometry Graduate Conference

Monday April 13, 2015

Tuesday April 14, 2015

Friday April 17, 2015

Wednesday April 22, 2015

Friday April 24, 2015

Tuesday April 28, 2015

Wednesday April 29, 2015

**Statistics Seminar**

Panel discussion

Stat faculty and students (UIC)

4:00 PM in SEO 636

This panel discussion will give students an opportunity to have questions about various things (e.g., advantages and disadvantages of
an academic career, general strategies for successful research, career opportunities outside of academia and how to prepare for them, etc)
answered by faculty and senior graduate students.

Friday May 1, 2015