# MSCS Seminar Calendar

Monday February 2, 2015

**Model Theory Seminar**

Weakly almost periodic functions, model-theoretic stability, and minimality of topological groups II

Gabriel Conant (UIC)

2:00 PM in SEO 427

We will continue discussing the paper "Weakly almost periodic functions, model-theoretic stability, and minimality of topological groups" by Ben-Yaacov and Tsankov.

**Algebraic topology seminar**

Characteristic classes in connective K-theory

Bob Bruner (Wayne State University)

3:00 PM in SEO 1227

We will describe the connective K-cohomology of U(n),
Sp(n), O(n), their oriented variants, the torus T(n) and the
'symplectic torus' Sp(1)^n, in so far as they are understood at present.
Variants include the equivariant and completed versions:
ku^*_G --> ku^*BG. They specialize to the usual integral homology
(at v=0) and to the representation theory (away from v=0). The best results are available for ku^* and the more highly connected
groups (e.g., Sp(n) rather than O(n)), but some results are available for
ko^* as well. We will start with some general facts about the relations between connective
K-theory, representation theory, and cohomology.

**Applied Mathematics Seminar**

Computation of three-dimensional standing water waves

Chris Rycroft (Harvard University)

4:00 PM in SEO 636

We develop a method for computing three-dimensional gravity-driven water waves, which we use to search for time-periodic standing wave solutions. We simulate an inviscid, irrotational, incompressible fluid bounded below by a flat wall, and above by an evolving free surface. The simulations require computing a velocity potential in the bulk of the fluid, which we carry out using a fourth-order finite element method; this computationally expensive step is solved using a parallel multigrid algorithm. Several families of large-amplitude three-dimensional standing waves are found in both shallow and deep regimes, and their physical characteristics will be examined and compared to previously known two-dimensional solutions.

Tuesday February 3, 2015

**Algebraic Geometry Seminar**

Boundary behavior of strata of holomorphic one-forms

Dawei Chen (Boston College)

3:00 PM in SEO 1227

Consider strata of holomorphic one-forms on Riemann surfaces with prescribed number and multiplicity of zeros. They define flat structures realizing the underlying surfaces as plane polygons whose boundary edges are identified suitably. In this talk, I will report some work in progress on degenerations of holomorphic one-forms in the same stratum when the underlying Riemann surfaces become nodal, with a focus on the interplay between algebraic geometry and flat geometry.

**Logic Seminar**

The asymptotic couple of the field of logarithmic transseries

Allen Gehret (UIUC)

4:00 PM in SEO 427

The differential-valued field $\mathbb{T}_{\log}$ of logarithmic transseries is conjectured to have good model theoretic properties. As a partial result in this direction, and as a
confidence building measure we prove that at least its \emph{asymptotic couple} has a good model theory. The value group $\Gamma_{\log}$ of $\mathbb{T}_{\log}$ can be given the additional
structure of a map $\psi:\Gamma\to\Gamma$ which is induced by the derivation on $\mathbb{T}_{\log}$. The structure $(\Gamma_{\log},\psi)$ is the asymptotic couple of the field of logarithmic
transseries (in the sense of Rosenlicht). In this talk we will discuss the good model-theoretic properties of $(\Gamma_{\log},\psi)$, including a quantifier-elimination result in an appropriate
first-order language, definable functions on a certain discrete set, a stable embedding result, and NIP (the Non-Independence Property). All results in this talk (besides NIP)
are in http://arxiv.org/abs/1405.1012.

Wednesday February 4, 2015

**Graduate Geometry, Topology and Dynamics Seminar**

Volume & Bounded Cohomology II: Measured homology and Thurston's Proof of Mostow rigidity.

Edgar A. Bering IV (UIC)

3:00 PM in SEO 612

Continuing from last time, where we introduced the Gromov norm on homology, we will introduce an alternate definition, characterize the Gromov norm of a hyperbolic manifold in terms of volume, and use this to prove Moscow rigidity for hyperbolic manifolds. References for this talk are the same as the previous week's.

Thursday February 5, 2015

Monday February 9, 2015

**Model Theory Seminar**

Weakly almost periodic functions, model-theoretic stability, and minimality of topological groups III

Joseph Zielinski (UIC)

2:00 PM in SEO 427

We will continue reading the paper "Weakly almost periodic functions, model-theoretic stability, and minimality of topological groups" by Ben Yaacov and Tsankov.

Wednesday February 11, 2015

Monday February 16, 2015

Wednesday February 18, 2015

Friday February 20, 2015

Monday February 23, 2015

Wednesday February 25, 2015

Friday February 27, 2015

Monday March 2, 2015

**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.

Wednesday March 4, 2015

**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

Friday March 13, 2015

Monday March 16, 2015

Wednesday March 18, 2015

Monday March 30, 2015

Wednesday April 1, 2015

Monday April 6, 2015

Wednesday April 8, 2015

Friday April 10, 2015

Monday April 13, 2015

Friday April 17, 2015

Wednesday April 22, 2015

Friday April 24, 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.