Archived Events

Monday, April 7, 2025, in the Alavi Commons from 4 to 5 p.m.
Automorphism Groups for Surfaces, Part II
Speaker: Gene Freudenburg

Monday, Mar 31, 2025, in the Alavi Commons from 4 to 5 p.m.
Automorphism Groups for Surfaces, Part I
Speaker: Gene Freudenburg

Monday, Mar 24, 2025, in the Alavi Commons from 4 to 5 p.m.
Irreducible representations of sl2(C) (Part 2)
Speaker: Lucy Mallory

Monday, Mar 10, 2025, in the Alavi Commons from 4 to 5 p.m.
The Miracle Octad Generator
Speaker: Professor David Richter

Monday, Feb 24, 2025, in the Alavi Commons from 4 to 5 p.m.
Hexacode, the Golay Code and the Mathieu groups, Part II
Speaker: Darryl Jent

Monday, Feb 17, 2025, in the Alavi Commons from 4 to 5 p.m.
Hexacode, the Golay Code and the Mathieu groups, Part I
Speaker: Darryl Jent

Monday, Feb 3, 2025, in the Alavi Commons from 4 to 5 p.m.
The loop G which is a Sharply 2-Transitive Group G on a set M: A Tale of Two Categories, Part II
Speaker: Professor Clifton Ealy

Friday, Jan 27, 2025, in the Alavi Commons from 4 to 5 p.m.
The loop G which is a Sharply 2-Transitive Group G on a set M: A Tale of Two Categories, Part I
Speaker: Professor Clifton Ealy

Friday, Jan 17, 2025, in the Alavi Commons from 4 to 5 p.m.
On Bilevel Variational Inequalities with Applications
Speaker: Oluwatosin T. Mewomo

Monday, Nov 25, 2024, in the Alavi Commons from 4 to 5 p.m.
Homogeneous Spaces for SL2(C) (Part 4)
Speaker: Professor Gene Freudenburg

Monday, Nov 11, 2024, in the Alavi Commons from 4 to 5 p.m.
Homogeneous Spaces for SL2(C) (Part 2)
Speaker: Professor Gene Freudenburg

Monday, Oct 28, 2024, in the Alavi Commons from 4 to 5 p.m.
Finite Subgroups of SL2(C) and their Binary Invariants (Part 3)
Speaker: Professor Gene Freudenburg

Monday, Oct 21, 2024, in the Alavi Commons from 4 to 5 p.m.
Finite Subgroups of SL2(C) and their Binary Invariants (Part 2)
Speaker: Professor Gene Freudenburg

Monday, Oct 7, 2024, in the Alavi Commons from 4 to 5 p.m.
Finite Subgroups of SL2(C) and their Binary Invariants (Part I)
Speaker: Professor Gene Freudenburg

Monday, Sept 30, 2024, in the Alavi Commons from 4 to 5 p.m.
Finite Groups of Quaternions and 4-Dimensional Regular Polytopes
Speaker: Professor David Richter

Monday, Sept 23, 2024, in the Alavi Commons from 4 to 5 p.m.
Finite Groups of Quaternions, Part three
Speaker: Professor David Richter

November 7, 2025 in Alavi Commons at 9 a.m.
Existence of Control Lyapunov Function for Asymptotically Controllable Nonlinear System
presented by Yuri Ledyaev, WMU Department of Mathematics

February 7, 2025 in Alavi Commons at 12 p.m.
Growth Optimal Portfolio with Rebalancing Cost
presented by Dr. Jim Zhu, WMU Department of Mathematics

November 4, 2024 in Alavi Commons at 9 a.m.
Neural Ordinary Differential Equations
presented by Matthew Allen Sutter, WMU Department of Mathematics

October 14, 2024 in Alavi Commons at 9 a.m.
Deep Learning, Backpropagation and Optimal Control
presented by Yuri Ledyaev, WMU Department of Mathematics

October 7, 2024 in Alavi Commons at 9 a.m.
A Linear Programming Model for Bank Balance Sheet Management Problems
presented by Dr. Jim Zhu in the WMU Department of Mathematics

September 30, 2024 via WebEx at 9 a.m.
Finite-Time Semistability and Consensus for Nonlinear Dynamical Networks presented by Yuri Ledyaev, WMU Department of Mathematics

April 10, 2023 
A one-sided version of the differential equation method presented by Dr. Patrick Bennett, Faculty in the WMU Department of Mathematics

April 3, 2023
Characterization of Convexity by using some Variational Properties presented by Abdul-Malik Saiid, Graduate student in the WMU Department of Mathematics

March 27, 2023
Case Study of the Longitudinal and Lateral Dynamics of Electric Vehicles presented by Ahmed Aly, First year master student in Computational and Applied Mathematics at WMU Department of Mathematics

March 13, 2023
On Two Different Series with the Same Properties presented by Dr. Radu Ioan Teodorescu, Emeritus Associate Professor in the WMU Department of Mathematics

February 27, 2023
Singular perturbations of control problems arising in global optimization for deep neural networks presented by Professor Martino Bardi, Mathematical Analysis professor at the University of Padova, Italy

February 20, 2023
Signals and Systems: The Part that Lebesgue Forgot to Tell You! presented by Dr. Frank Severance, Professor Emeritus of WMU Electrical and Computer Engineering

February 13, 2023
Optimal Control in a Model of Dendritic Cell Transfection Cancer Immunotherapy (after F. Castiglione and B. Piccoli) presented by Matthew Allen Sutter, Graduate student in the WMU Applied and Computational Mathematics program

February 6, 2023
Modern Koopman Theory for Dynamical Systems II (after S.L. Brunton, M. Budisic, E. Kaiser, J.N. Kurtz) presented by Yuri S. Ledyaev, Professor in the WMU Mathematic Department

January 30, 2023
Modern Koopman Theory for Dynamical Systems (after S.L. Brunton, M. Budisic, E. Kaiser, J.N. Kurtz) presented by Yuri S. Ledyaev, Professor in the WMU Mathematic Department

January 23, 2023
Analysis and Applied Mathematics Seminar Organizational Meeting presented by Yuri S. Ledyaev, Professor in the WMU Mathematic Department

Monday, Oct. 14, 2024

Cages and Finite Geometries by Dr. Gariela Araujo-Pardo, Instituto de Matemáticas de la Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México

Time: 4 p.m. Refreshments served at 3:45 p.m.

Thursday, Mar. 16, 2023

Imaging and Struggling Toward Enriching Futures with Disabilities in and through Mathematics Education: The Roles of Intersectional Justice and Anti-ableism presented by Dr. Paulo Tan, University of Missouri-St Louis

Time: 4 to 5 p.m.

Abstract: Historically, disabled students have been dehumanized in education. Typically in schools, they are only offered access to low-rigor learning that emphasizes rote procedures and narrow skills, and are often segregated physically and socially from their non-disabled peers. Scholars and activists have called for the humanization of disabled students via anti-ableist and antiracist struggle toward systemic transformation. In this presentation, Dr. Tan shares how intersectional justice and anti-ableist stances can support mathematics educators in co-imagining and co-struggling toward enriching futures with disabilities. Flyer

Thursday, Feb. 20, 2020

A Eureka Moment in the Theory of Commutators, Operators of the Form AB - BA, History and Consequences presented by Gary Weiss, Ph.D., University of Cincinnati

Time: 4:00 p.m. Refreshments served at 3:50 p.m.

Abstract: Understanding operators on Hilbert space of the form AB-BA is essential in many parts of operator theory and its applications. This talk will describe some early problems and consequences of their solutions. But the focus will be on the evolution of a key simple sounding commutator question about a special 4 x 4 matrix and the evolution of its solution and its consequential complete characterizations of Hilbert space commutators.

Thursday, Nov. 14, 2019

Tropical Principal Component Analysis on Tree Spaces presented by Ruriko Yoshida, Ph.D., Naval Postgraduate School

Time: 4:00 p.m. Refreshments served at 3:50 p.m.

Abstract: In 2004, Speyer and Sturmfels showed that a space of phylogenetic trees with fixed set of leaves is a tropical linear space defined by the tropicalization of linear equations. It is thus natural to apply tropical arithmetics to conduct statistical analyses over a tree space under the tropical metric, such as tropical principal component analysis (PCA). We discuss tropical PCA as a tropical polytope which minimizes the sum of residuals over a tree space. We then apply this to several empirical datasets.

Thursday, Nov. 7, 2019

Responding to Students' Mathematical Thinking During Collaborative Problem Solving presented by Jen Munson, Ph.D., Northwestern University

Time: 4:00 p.m. Refreshments served at 3:50 p.m.

Abstract: While a great deal of attention has been paid to the ways that math teachers can facilitate productive discussions at the end of a lesson, little research has explored how teachers uncover and respond to student thinking during collaborative problem solving. In this talk, I'll share results from a study that characterized interactions in which teachers go beyond eliciting student thinking in the moment, to responding in ways that nudge student thinking forward.

Thursday, Oct. 24, 2019

The Structure and Interpretation of Graph Spectral Densities presented by David Bindel, Ph.D., Cornell University

Time: 4:00 p.m.& Refreshments served at 3:50 p.m.

Abstract: In this talk, we analyze graphs via global summaries of eigenvalue distributions and eigenvector behavior. Our approach draws from condensed matter physics, where the idea of local and global densities of states is used to understand the electronic structure of systems. We describe how these densities play a common role in such seemingly disparate topics as spectral geometry, condensed matter physics and the study of centrality measures in graphs. We also discuss algorithms to estimate spectral densities.

Friday, Oct. 11, 2019

The Role of Productive Struggle in Learning Math presented by Kevin Dykema, Mattawan Schools

2019 Mathematics Alumni Award Recipient

Time: 3:00 p.m. Refreshments served at 2:50 p.m.

Abstract: In 2014, the National Council of Teachers of Mathematics released 8 research-informed mathematics teaching practices with its publication of Principles to Actions. One of those 8 is supporting productive struggle in learning math, which provides a name to what many have done for years. Kevin will share his journey of learning about and implementing productive struggle through experiences as a middle school classroom teacher, graduate student at WMU, conducting professional development throughout the United States, involvement with Michigan Council of Teachers of Mathematics and the National Council of Teachers of Mathematics as board members.

Apr. 11, 2025

Chvatal's t0- tough conjecture
presented by Linda Lesniak at 10 a.m. in the Alavi Commons 6625 Everett Tower

Mar. 28, 2025

The Ramsey Index of a Graph II
presented by Ritabrato Chatterjee at 10 a.m. in the Alavi Commons 6625 Everett Tower

Mar. 21, 2025

Forbidden Subgraphs of Single Graphs
presented by Allan E. Bickle at 10 a.m. in the Alavi Commons 6625 Everett Tower

Feb. 21, 2025

From a Chessboard Problem to a Graph Coloring Problem 
presented by Sawyer Osborn at 10 a.m. in the Alavi Commons 6625 Everett Tower

Feb. 14, 2025

The Ramsey Inex of a Graph 
presented by Sawyer Osborn at 10 a.m. in the Alavi Commons 6625 Everett Tower

Feb. 7, 2025

Multiple Monochromatic Subgraphs in Edge-Colored Graphs 
presented by Emma Jent at 10 a.m. in the Alavi Commons 6625 Everett Tower

Jan. 31, 2025

On the genus of the simple groups PSL(2,q), PSL(3,q) and PSp(4,q) a brief organization meeting presented by Clifton E. ealy Jr. at 10 a.m. in the Alavi Commons 6625 Everett Tower

Nov. 12, 2024

Ehrhart Polynomials of Generic Orthotopes presented by David Richter at 10 a.m. in the Alavi Commons 6625 Everett Tower

Nov. 5, 2024

An Overview of the History and Application of Ramsey Theory presented by Emma Jent at 10 a.m. in the Alavi Commons 6625 Everett Tower

Oct. 29, 2024

A Natural Extension of Ramsey Numbers presented by Emma Jent at 10 a.m. in the Alavi Commons 6625 Everett Tower

Oct. 22, 2024

Yes, there really is a Kalamazoo: Western Michigan University - Graph Theory 1968-2000 presented by Linda Lesniak at 10 a.m. in the Alavi Commons 6625 Everett Tower

Oct. 15, 2024

On Mixed Graphs presented by Gabriela Araujo-Pardo from Universidad Nacional Aut´onoma de M´exico, Campus Juriquilla, Quer´etaro. M´exico

Feb. 5, 2020

The so-called differential equation method in probabilistic combinatorics presented by Patrick Bennett, Ph.D., Department of Mathematics, Western Michigan University

Abstract: Differential equations inherently belong to the realm of continuous mathematics, but often they are used to describe discrete objects. For example, we use differential equations to model population growth (and the size of a population is always an integer). In this talk I will describe a general method for proving that certain random processes are overwhelmingly likely to evolve in a way that is very closely approximated by a solution to a system of differential equations. Several examples will be discussed.

Jan. 29, 2020

Anti-van der Waerden numbers on Trees presented by Elizabeth Sprangel, Iowa State University

Abstract: In this talk, arithmetic progressions on the integers and the integers modulo n are extended to graphs. This allows for the definition of the anti-van derWaerden number of a graph, which is the least positive integer r such that every exact r-coloring of a graph contains a rainbow k-term arithmetic progression. We will discuss bounds on the anti-van der Waerden number on trees regarding 3-term arithmetic progressions.

Jan. 15, 2020

Hamiltonian Berge Cycles in Random Hypergraphs presented by Deepak Bal, Ph.D., Montclair State University

Abstract: A Berge cycle in a hypergraph is an alternating sequence of distinct vertices and edges (v₁, e₁, ... , v_n, e_n) where v_i+1 are in e_i for each i (indices considered modulo n), and a Hamiltonian Berge cycle is one in which every vertex appears. In this talk we will discuss the threshold probability for when a random r-uniform hypergraph is likely to contain such a cycle. This is joint work with Pat Devlin, Ross Berkowitz and Mathias Schacht.

Nov. 20, 2019

Te size-Ramsey number of a path presented by Louis DeBiasio, Ph.D., Miami University

Abstract: Given a graph H, the size-Ramsey number of H is the minimum m such that there exists a graph G with m edges such that in every 2-coloring of G, there exists a monochromatic copy of H. Perhaps due to the fact that Paul Erdös offered $100 simply to determine the correct order of magnitude, getting bounds on the size-Ramsey number of P_n, the path on n vertices, is the most well-studied case. It is known that the size-Ramsey number of P_n is between (2.5 - o(1))n and 74n, with the current best upper and lower bounds both due to Dudek and Pralat.

We prove that every graph with at most (3.75 - o(1))n edges has a 2-coloring such that there are no monochromatic P_n's, which shows that the size-Ramsey number of P_n is at least (3.75 - o(1))n. We also discuss the r-color version of the problem.

Joint work with Deepak Bal.

Nov. 14, 2019

Maximum Crossing Numbers of Trees and Weighted Turan Numbers presented by Sean English, Ph.D., Department of Mathematics, University Of Illinois At Urbana-Champaign

3 p.m.

Nov. 6, 2019

Alternating Connectivity in Random Graphs, Part II presented by Ryan Cushman, Department of Mathematics, Western Michigan University

Abstract: This talk will be a continuation of last week's talk. In the noisy channel model from coding theory, we wish to detect errors introduced during transmission by optimizing various parameters of the code. For example, it is advantageous to find codes in which code words do not share many corresponding digits (i.e. code words have a large Hamming distance). Thus, one may ask what the maximum n is such that there exists a code of n code words with a fixed alphabet, code words with m digits, and minimum Hamming distance t. We can translate this context into the language of complete bipartite graphs K_m,n. In this translation, finding the Hamming distance between two code words corresponds to counting the number of alternating paths between corresponding vertices. Bennett, Dudek, and LaForge considered a related problem of maximizing the number of internally disjoint alternating paths between any two vertices in a certain partition set. In this talk, we discuss the current state of the question as well as a generalization for G(n,p).

Oct. 30, 2019

Alternating Connectivity in Random Graphs presented by Ryan Cushman, Department of Mathematics, Western Michigan University

Abstract: In the noisy channel model from coding theory, we wish to detect errors introduced during transmission by optimizing various parameters of the code. For example, it is advantageous to find codes in which code words do not share many corresponding digits (i.e. code words have a large Hamming distance). Thus, one may ask what the maximum n is such that there exists a code of n code words with a fixed alphabet, code words with m digits, and minimum Hamming distance t. We can translate this context into the language of complete bipartite graphs K_m,n. In this translation, finding the Hamming distance between two code words corresponds to counting the number of alternating paths between corresponding vertices. Bennett, Dudek, and LaForge considered a related problem of maximizing the number of internally disjoint alternating paths between any two vertices in a certain partition set. In this talk, we discuss the current state of the question as well as a generalization for G(n,p).

Oct. 9, 2019

Bears versus the demon on Kn,n, part II presented by Patrick Bennett, Ph.D., Department of Mathematics, Western Michigan University

Abstract: In this talk we will finish describing a strategy for the bears in the Hat Guessing Game (the game is described below), which appeared in a recent paper by Alon, Ben-Eliezer, Shangguan and Tamo. Last week we proved that the existence of certain matrices would imply a strategy for the bears on K_n,n. We say a q-ary matrix is t-saturated of for every set T of t columns there exists a row in which the columns of T have every entry in {1,...,q}. We will prove the existence of t-saturated q-ary matrices of a suitable dimension to be used for a strategy for the bears in the Hat Guessing Game. Then, time permitting, we will discuss ideas for the Hat Guessing Game on K_n,n,n.

The Hat Guessing Game is as follows: There are n bears and one demon (who can read the bears' minds), and the bears are each sitting on one vertex of a graph G. The bears close their eyes and the demon chooses one colored hat for each bear, where each hat can be one of q different colors. The bears open their eyes and they can see the hats of their neighbors (in G). Without communicating with each other, the bears will now each guess the color of their own hats. The guesses are made simultaneously so one bear's guess cannot depend on another's. The bears win if any of them guess correctly; the demon wins if the bears are all incorrect. Clearly the bears have a winning strategy if q = 1, and last week we showed the demon has a winning strategy if q > n. We define HG(G) to be the largest q such that the bears win.

Oct. 2, 2019

Bears versus the demon on K presented by Patrick Bennett, Ph.D., Department of Mathematics, Western Michigan University

Abstract: consider the following puzzle. Suppose there are n bears and one demon (who can read the bears' minds). The bears close their eyes and the demon chooses one colored hat for each bear, where each hat can be one of q different colors. The bears open their eyes and they can see all the other bears hats, but not their own hat. Without communicating with each other, the bears will now each guess the color of their own hats. The guesses are made simultaneously so one bear's guess cannot depend on another's. The bears win if any of them guess correctly; the demon wins if the bears are all incorrect. In this situation, it is known that the bears have a winning strategy if and only if q ≤ n.

In 2008, Butler, Hajiaghayi, Kleinberg and Leighton generalized the above puzzle. Now we suppose each bear sits at a vertex in a graph, and the bears can only see their neighbors' hats. We can now ask for any graph, what is the maximum q for which the bears have a winning strategy. In this talk we will try to focus on the case where the graph is K_n,n and a new lower bound proved by Alon, Ben-Eliezer, Shangguan and Tamo.

Sept. 18, 2019

Combinatorial Nullstellensatz presented by Patrick Bennett, Ph.D., Department of Mathematics, Western Michigan University

Abstract: In 1999, Noga Alon proved the combinatorial Nullstellensatz (a theorem about the zeroes of polynomials over fields) and gave some surprising applications. In this talk we will state the Nustellensatz and then see several of these applications.

Sept. 11, 2019

Long monochromatic paths in random graphs presented by Andrzej Dudek, Ph.D., Department of Mathematics, Western Michigan University

Abstract: Recall that the size-Ramsey number of F, r^(F, r), is the smallest integer m such that there exists a host graph G with m edges such that any r-edge coloring of G yields a monochromatic copy of F. In this talk, we are concerned with the size-Ramsey numbe3r of the path P_n on n vertices. First, we explore some recent developments regarding r^(P_n, r). Next, we study a Turán problem involving random graphs G(N, p), the best-known host graphs for P_n. To that end, we consider the random variable ex(G(N, p), P_n), the maximum number of edges in a P_n-free subgraph of G(N, p). The latter is a joint work with József Balogh and Lina Li (University of Illinois at Urbana-Champaign).