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Friday, June 30, 2023 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Andy Zucker

Title: Ramsey degrees, big and small

Speaker: Andy Zucker
Affiliation: University of Waterloo
Location: MC 5501

Abstract: Many of the seminal results in finite Ramsey theory can be phrased by saying that a certain class of finite structures has the Ramsey property, such as the ordinary finite Ramsey theorem (the class of finite linear orders), the dual Ramsey theorem (the class of finite lex-ordered Boolean algebras), the Graham-Leeb-Rothschild theorem (the class of lex-ordered, finite-dimensional vector spaces over a fixed finite field), and the Nesetril-Rodl theorem (the class of finite ordered triangle-free graphs, among many others).

Tuesday, July 4, 2023 2:30 pm - 2:30 pm EDT (GMT -04:00)

URA Seminar - Bethany Caldwell

Title: Douglas–Rachford Algorithm for Control- and State-constrained Optimal Control Problems

Speaker: Bethany Caldwell
Affiliation: University of Waterloo
Location: MC 5501

Abstract: The Douglas - Rachford algorithm has been applied to many optimization problems due to its simplicity and efficiency but the application of this algorithm to optimal control is less common. In this talk we utilize this method to solve state- and control-constrained linear-quadratic optimal control problems.

Thursday, July 6, 2023 1:00 pm - 1:00 pm EDT (GMT -04:00)

Algebraic Combinatorics - Ben Webster

Title: Modular representations of the symmetric group and categorification (part I)

Speaker: Ben Webster
Affiliation: University of Waterloo/Perimeter Institute
Location: MC 5501 and Zoom - please contact Oliver Pechenik for the Zoom link

Abstract: I'll give two talks on the representations of the symmetric group over small finite fields, in particular, their block structure, with an emphasis on the perspective from categorical actions of Lie algebras.  No previous background in modular representation theory will be assumed.  

Friday, July 7, 2023 3:30 pm - 3:30 pm EDT (GMT -04:00)

Distinguished Tutte Lecture - Jacob Fox

Title: Ramsey Cayley graphs, random graph models, and information theory

Speaker: Jacob Fox
Affiliation: Stanford University
Location: MC 5501

Abstract: A graph is Ramsey if its largest clique or independent set is of size logarithmic in the number of vertices. While almost all graphs are Ramsey, there is still no known explicit construction of Ramsey graphs. Alon conjectured that every finite group has a Ramsey Cayley graph.

Monday, July 10, 2023 1:00 pm - 1:00 pm EDT (GMT -04:00)

C&O Reading Group - Rian Neogi

Title: Budget Feasible Mechanisms

Speaker: Rian Neogi
Affiliation: University of Waterloo
Location: MC 6029

Abstract: In the setting of budget feasible mechanism design, a buyer wants to purchase items from a set of agents. Each agent can supply at item at an incurred cost of c_i to themself, and the buyer wants to optimize over their own valuation for the set of items bought. The cost c_i is private information that the buyer doesn't have access to. The goal is to design a mechanism that is truthful, in the sense that the sellers do not have incentive to deviate from reporting their true costs, and budget feasible, in the sense that the total payments made to the sellers is within some budget B.

Monday, July 10, 2023 2:30 pm - 2:30 pm EDT (GMT -04:00)

URA Seminar - Shayla Redlin Hume

Title: Counting matroid extensions

Speaker: Shayla Redlin Hume
Affiliation: University of Waterloo
Location: MC 5479

Abstract: In this talk, we will discuss methods of counting the number of extensions of certain matroids. We will see that, in some cases, the number of extensions is surprisingly large. I will start by introducing matroids, so previous experience with matroids is not assumed.

Monday, July 10, 2023 8:00 pm - 8:00 pm EDT (GMT -04:00)

Algebraic Graph Theory - Xiaoye Liang

Title: Thin distance-regular graphs with classical parameters $(D,q,q,\frac{q^{t}-1}{q-1}-1)$ with $t> D$ are the Grassmann graphs

Speaker: Xiaoye Liang
Affiliation: Anhui Jianzhu University
Location: Please contact Sabrina Lato for Zoom link

Abstract: In the survey paper by Van Dam, Koolen and Tanaka (Distance-regular graphs, Electron. J. Comb., Dynamic Survey (2016), \#DS22), they asked to classify the thin $Q$-polynomial distance-regular graphs. In this talk, we will discuss our result which states that the Grassmann graphs with large diameter are characterized by their intersection numbers under the extra condition that they are thin.

This is joint work with Jack Koolen and Ying-Ying Tan.

Monday, July 17, 2023 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory - Himanshu Gupta

Title: On the eigenvalues of the graphs D(5,q)

Speaker: Himanshu Gupta
Affiliation: University of Delaware
Location: Please contact Sabrina Lato for Zoom link

Abstract: In 1995, Lazebnik and Ustimenko introduced the family of q-regular graphs D(k, q), which is defined for any positive integer k and prime power q. The connected components of the graph D(k, q) have provided the best-known general lower bound on the size of a graph for any given order and girth to this day.

Monday, July 17, 2023 1:00 pm - 1:00 pm EDT (GMT -04:00)

C&O Reading Group - Rian Neogi

Title: Budget Feasible Mechanisms : Part II

Speaker: Rian Neogi
Affiliation: University of Waterloo
Location: MC 6029

Abstract: In the setting of budget feasible mechanism design, a buyer wants to purchase items from a set of agents. Each agent can supply at item at an incurred cost of c_i to themself, and the buyer wants to optimize over their own valuation for the set of items bought. The cost c_i is private information that the buyer doesn't have access to. The goal is to design a mechanism that is truthful, in the sense that the sellers do not have incentive to deviate from reporting their true costs, and budget feasible, in the sense that the total payments made to the sellers is within some budget B.

Monday, July 17, 2023 2:30 pm - 2:30 pm EDT (GMT -04:00)

URA Seminar - Rian Neogi

Title: Budget Feasible Mechanisms

Speaker: Rian Neogi
Affiliation: University of Waterloo
Location: MC 5479

Abstract: In the setting of budget feasible mechanism design, a buyer wants to purchase items from a set of agents. Each agent can supply at item at an incurred cost of c_i to themself, and the buyer wants to optimize over their own valuation for the set of items bought. The cost c_i is private information that the buyer doesn't have access to. The goal is to design a mechanism that is truthful, in the sense that the sellers do not have incentive to deviate from reporting their true costs, and budget feasible, in the sense that the total payments made to the sellers is within some budget B.