# Seminars and Colloquia

## Other

Apr 12

#### Mathematics Colloquium

04:20 pm

Aaron Brown, University of Chicago Recent progress in the Zimmer program Abstract: The Zimmer program refers to a number of questions and conjectures about actions of certain discrete groups, namely, lattices in higher-rank simple Lie groups. The primary example example of a such a group is SL(n,R). In the past few years, there has been significant progress in the Zimmer program. In my talk, I will discuss a recent proof of Zimmer's conjecture which shows that (cocompact and certain non-uniform) higher-rank lattices do not act on manifolds with low dimension. I will also discuss recent results and work in progress that classify all possible non-trivial actions under certain dynamical or dimension assumptions.

Nov 30

#### PCSE/IDEAS: Programmers Summit

12:00 pm

By invitation only. Contact mjkingsley@wesleyan.edu to learn more.

Nov 10

#### KrisTapp Talk

12:00 pm

Wesleyan's Undergrad Math Club Presents: The Math of Gerrymandering Abstract:In Gill v. Whitford , a Wisconsin court struck down the state assembly map as unconstitutional gerrymandering. Will the US Supreme court uphold this landmark ruling? The plaintiffs case hinges on elementary mathematics, including a simple new efficiency gap formula that attempts to measure gerrymandering. For deciding whether this formula works, a few highly relevant mathematical facts were discovered so recently, the Supreme Court probably doesnt know about them. But you will if you attend this talk. No math or political science background will be assumed.

Nov 8

#### Computer Science Open House

12:00 pm

Nov 1

#### Mathematics Open House

12:00 pm

Oct 26

#### Ann Guo Talk

12:00 pm

Wesleyan's Undergrad Math Club Presents: Ann Guo Career Engineering 101 Come learn how to design, build, and test careers that will fulfill your passions while considering the limitations imposed by parents, society, and studentloans. Ann is an MIT-trained computer scientist who eventually found her calling as a career coach. In between, she ran global campus recruiting at analgorithmic trading firm where she gained insider knowledge on the hiring process. At Passion Analytics, she is developing an automated online careercoach to help people at scale. Ann holds BS & MEng degrees in Computer Science from MIT and PhD from UMass Amherst. Lunch will be served!

Oct 22

#### MAMLS Conference

09:00 am

The Mid-Atlantic Mathematical Logic Seminar, supported by the NSF, will start its 2017-2018 season at Wesleyan University. 8 distinguished researchers will give 50-minute lectures, many on model theory, over the course of a day and a half. Day 2 Schedule: 9-9:50: Alexandra Shlapentokh, "The Definability World in Number Theory." 10:30-11:20: Philipp Rothmaler, "Pure submodules of direct products of finitely presented modules." 11:30-12:20: Deirdre Haskell, "Residue field domination in theories of valued fields."

Oct 21

#### MAMLS Conference

09:00 am

the Mid-Atlantic Mathematical Logic Seminar, supported by the NSF, will start its 2017-2018 season at Wesleyan University. 8 distinguished lecturers will give 50-minute lectures, many on model theory, over the course of a day and a half. Day 1: 9-9:50: Alex Kruckman, "Generic theories, independence, and NSOP1." 10:30-11:20: Sergei Starchenko, "The topological closure of algebraic and semi-algebraic flows on complex and real tori." 11:30-12:20: Hans Schoutens, "Defining affine n-space." 2:30-3:20: Alice Medvedev, "Feferman-Vaught and the Product of Finite Fields." 4-4:50: Pierre Simon, "Finitely generated dense subgroups of automorphism groups."

Mar 8

#### Google Recruiting Event

04:30 pm

Dec 8

#### Class; Math Club Hill

12:00 pm

Wesleyans Undergrad Math Club presents: Professor Cameron Hill Very Large Networks In the last few decades, we have found that many of the most interesting structures and phenomena around can be described as networks. Examples of these include the Internet, the human brain, computer processors/chips, and many others. So, a network is a just system of discrete elements with connections/interactions between them. When investigating a very large network (e.g. the human brain has something like a hundred billion neurons), it is infeasible to examine each node individually, and even ``looking at the whole network at once is either impossible or basically meaningless. In this situation, we have to settle for examining either ``global processes on the network (which sort of, kind of, allow calculus to make sense) or random local sampling. These options raise several questions like, ``When can we guarantee that random local sampling is not lying to us? and ``Does random local sampling secretly have something to do with global processes? In this talk, I will make some of this stuff a bit more formal and principled, and I will try to explain how we are beginning to address and settle these questions.

Sep 28

#### Wesleyan CS Club - First Meeting

07:00 pm

The Wesleyan CS Club is having its first official meeting of the semester. We'll be talking about hackathons, projects and summer internships! Old and new members are welcome to attend. Non CS majors also extremely welcome. Wednesday 28th September , ESC 339. 7pm .

Apr 15

#### Mini-course in Mathematics: Dave Witte Morris (University of Lethbridge, Canada)

01:10 pm

TALK #1: What is an arithmetic group? Wednesday 4/13 Exley 121 4:15pm-5:15pm ABSTRACT: We will discuss a few basic properties of "arithmetic groups,'' which are certain groups of matrices with integer entries. By definition, the subject combines algebra (group theory and matrices) with number theory (the integers), but it also has connections with other areas, including the theory of periodic tilings. The three talks in this series are almost entirely independent of each other, so it will be perfectly feasible to attend any subset. ------------------------------------------------------------ TALK #2: Some arithmetic groups that cannot act on the line Thursday 4/14 Exley 121 4:15pm-5:15pm ABSTRACT: It is known that finite-index subgroups of the arithmetic group SL(3,Z) have no (orientation-preserving) actions on the real line. This naturally led to the conjecture that most other arithmetic groups also cannot act on the line. This problem remains open, but it can be solved in cases where every element of the group is a product of a bounded number of elementary matrices. No familiarity with arithmetic groups will be assumed. ------------------------------------------------------------ TALK #3: What is an amenable group? Friday 4/15 Exley 121 1:10pm-2:10pm ABSTRACT: Amenability is a fundamental notion in group theory, as evidenced by the fact that it can be defined in more than a dozen different ways. A few of these different definitions will be discussed, and we will see how amenability arises in the study of arithmetic groups. To learn more about arithmetic groups (and the role played by amenable groups), download a free copy of the speaker's book from http://arxiv.org/src/math/0106063/anc/

Apr 14

#### Mini-course in Mathematics: Dave Witte Morris (University of Lethbridge, Canada)

04:15 pm

TALK #1: What is an arithmetic group? Wednesday 4/13 Exley 121 4:15pm-5:15pm ABSTRACT: We will discuss a few basic properties of "arithmetic groups,'' which are certain groups of matrices with integer entries. By definition, the subject combines algebra (group theory and matrices) with number theory (the integers), but it also has connections with other areas, including the theory of periodic tilings. The three talks in this series are almost entirely independent of each other, so it will be perfectly feasible to attend any subset. ------------------------------------------------------------ TALK #2: Some arithmetic groups that cannot act on the line Thursday 4/14 Exley 121 4:15pm-5:15pm ABSTRACT: It is known that finite-index subgroups of the arithmetic group SL(3,Z) have no (orientation-preserving) actions on the real line. This naturally led to the conjecture that most other arithmetic groups also cannot act on the line. This problem remains open, but it can be solved in cases where every element of the group is a product of a bounded number of elementary matrices. No familiarity with arithmetic groups will be assumed. ------------------------------------------------------------ TALK #3: What is an amenable group? Friday 4/15 Exley 121 1:10pm-2:10pm ABSTRACT: Amenability is a fundamental notion in group theory, as evidenced by the fact that it can be defined in more than a dozen different ways. A few of these different definitions will be discussed, and we will see how amenability arises in the study of arithmetic groups. To learn more about arithmetic groups (and the role played by amenable groups), download a free copy of the speaker's book from http://arxiv.org/src/math/0106063/anc/

Apr 13

#### Mini-course in Mathematics: Dave Witte Morris (University of Lethbridge, Canada)

04:15 pm

TALK #1: What is an arithmetic group? Wednesday 4/13 Exley 121 4:15pm-5:15pm ABSTRACT: We will discuss a few basic properties of "arithmetic groups,'' which are certain groups of matrices with integer entries. By definition, the subject combines algebra (group theory and matrices) with number theory (the integers), but it also has connections with other areas, including the theory of periodic tilings. The three talks in this series are almost entirely independent of each other, so it will be perfectly feasible to attend any subset. ------------------------------------------------------------ TALK #2: Some arithmetic groups that cannot act on the line Thursday 4/14 Exley 121 4:15pm-5:15pm ABSTRACT: It is known that finite-index subgroups of the arithmetic group SL(3,Z) have no (orientation-preserving) actions on the real line. This naturally led to the conjecture that most other arithmetic groups also cannot act on the line. This problem remains open, but it can be solved in cases where every element of the group is a product of a bounded number of elementary matrices. No familiarity with arithmetic groups will be assumed. ------------------------------------------------------------ TALK #3: What is an amenable group? Friday 4/15 Exley 121 1:10pm-2:10pm ABSTRACT: Amenability is a fundamental notion in group theory, as evidenced by the fact that it can be defined in more than a dozen different ways. A few of these different definitions will be discussed, and we will see how amenability arises in the study of arithmetic groups. To learn more about arithmetic groups (and the role played by amenable groups), download a free copy of the speaker's book from http://arxiv.org/src/math/0106063/anc/

Apr 11

#### Seminar/Colloquium: Coven/Wood Lecture Series in Mathematics

04:00 pm

Maria Chudnovsky, Professor of Mathematics and PACM at Princeton University "Induced Subgraphs and Coloring" Abstract: The Strong Perfect Graph Theorem states that graphs with no no induced odd cycle of length at least five, and no complements of one behave very well with respect to coloring. But what happens if only some induced cycles (and no complements) are excluded? Gyarfas made a number of conjectures on this topic, asserting that in many cases the chromatic number is bounded by a function of the clique number. In this talk we discuss recent progress on some of these conjectures. This is joint work with Alex Scott and Paul Seymour.

Apr 8

#### Seminar/Colloquium: Coven/Wood Lecture Series in Mathematics

04:00 pm

Maria Chudnovsky, Professor of Mathematics and PACM, Princeton University "Some Problems in Graph Theory" Abstract: In this talk we will survey a few classical problems in graph theory, and explore their relationship to the fields of research that are active today. In particular, we will discuss Ramsey theory, graph coloring, perfect graphs, as well as some more recent research directions.

Nov 10

#### Wesleyan's Undergrad Math Club presents: Professor Karen Collins "Graphs and symmetries"

12:00 pm

Abstract: Many objects in nature have symmetry. Orb web spiders, for instance, create nearly perfect circular webs. Snowflakes have 6-fold radial symmetry, and humans have bilateral symmetry. The set of symmetries of a fixed object form a (mathematical) group, which is a set with a binary relation that is closed, associative, and has an identity element and inverses. Looking at the situation in reverse, every group describes some set of symmetries. Thus, the question arises: for any finite group G, is there an object whose group of symmetries is G? We will answer this question using tools from graph theory.