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Monday, April 3, 2023 11:30 am - 11:30 am EDT (GMT -04:00)

algebraic Graph Theory - Monu Kadyan

Title: Four types of integrality on mixed Cayley graphs over abelian groups

Speaker: Monu Kadyan
Affiliation: Indian Institute of Technology Guwahati
Location: Please contact Sabrina Lato for Zoom link

Abstract: A mixed graph is called H-integral (resp. HS-integral) if the eigenvalues of its Hermitian-adjacency matrix (resp. Hermitian-adjacency matrix of second kind) are integers.

Monday, April 3, 2023 3:00 pm - 3:00 pm EDT (GMT -04:00)

Graph and Matroids Seminar - Alvaro Carbonero

Title: The heroes of digraphs: coloring digraphs with forbidden induced subgraphs

Speaker: Alvaro Carbonero
Affiliation: University of Waterloo
Location: MC 5479

Abstract: The chromatic number is one of the most studied graph invariants in graph theory. $\chi$-boundedness, for instance, studies the induced subgraphs present in graphs with large chromatic number and small clique number. Neumann-Lara introduced an analog directed version of this graph invariant: the dichromatic number of digraphs.

Monday, April 10, 2023 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory - Andrew Jena

Title: Quantum Algorithms and Mutually Unbiased Bases

Speaker: Andrew Jena
Affiliation: University of Waterloo
Location: Please contact Sabrina Lato for Zoom link

Abstract: Mutually unbiased bases are fundamental to quantum information theory, showing up in quantum key distribution, quantum error correction, and quantum entanglement measures. They likewise might be familiar to algebraic graph theorists, thanks to their connection to equiangular lines and association schemes.

Friday, April 14, 2023 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Peter Winkler

Title: Sets that Support a Joint Distribution

Speaker: Peter Winkler
Affiliation: Dartmouth College
Location: MC 5501 or contact Eva Lee for Zoom link

Abstract: Given a closed set on the plane and two probability distributions on the real line, when are there random variables with the given distributions whose joint distribution is supported by the given set?

Monday, April 24, 2023 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory - Nathan Benedetto Proenca

Title: A Primal-Dual Extension of the Goemans and Williamson Algorithm for Weighted Fractional Cut Cover

Speaker: Nathan Benedetto Proenca
Affiliation: University of Waterloo
Location: Please contact Sabrina Lato for Zoom link

Abstract: A cut in a graph G = (V, E) is a set of edges which has one endpoint in S, for a given subset S of V. The fractional cut-covering number is the optimal value of a linear programming relaxation for the problem of covering each edge by a set of cuts. Beyond its role as part of Šámal's work on cut continuous functions, this graph parameter also arises as the gauge dual of the maximum cut problem.

Monday, May 1, 2023 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory - Sjanne Zeijlemaker

Title: On the diameter and zero forcing number of some graph classes in the Johnson, Grassmann and Hamming association scheme

Speaker: Sjanne Zeijlemaker
Affiliation:

Eindhoven University of Technology

Location: Please contact Sabrina Lato for Zoom link

Abstract:  Graph classes in the Johnson, Grassmann and Hamming association scheme have received a considerable amount of attention over the last decades. Although several (NP-hard) graph parameters have been investigated for these families, many remain unknown. In this talk, we establish the diameter of generalized Grassmann graphs, extending previous results for generalized Johnson graphs.

Monday, May 15, 2023 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory - Yuval Filmus

Title: Orthogonal basis of eigenvectors for the Johnson and Kneser graphs

Speaker: Yuval Filmus
Affiliation: Technion
Location: Please contact Sabrina Lato for Zoom link

Abstract: The Johnson and Kneser graphs have the same eigenspaces. How explicitly can we describe these eigenspaces? 

Friday, May 19, 2023 3:30 pm - 3:30 pm EDT (GMT -04:00)

Distinguished Tutte Lecture - Petter Brändén

Title: Lorentzian polynomials

Speaker: Petter Brändén
Affiliation: KTH Royal Institute of Technology
Location: MC 5501 

Abstract: Lorentzian polynomials on cones are intimately connected to Hodge theory, matroid theory and the geometry of zeros of polynomials.

Friday, May 26, 2023 1:30 pm - 1:30 pm EDT (GMT -04:00)

Continuous Optimization Seminar - Kay Barshad

Title: Generalized Modular String Averaged Procedure and Its Applications to Iterative Methods

Speaker: Kay Barshad
Affiliation: University of Waterloo
Location: MC 6029

Abstract: A modular string averaging procedure (MSA, for short) for a finite number of operators  was first introduced by Reich and Zalas in 2016. The MSA concept provides a flexible  algorithmic framework for solving various feasibility problems such as common fixed point and convex feasibility problems.

Friday, May 26, 2023 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Wouter Castryck

Title: Breaking the Supersingular Isogeny Diffie-Hellman protocol

Speaker: Wouter Castryck
Affiliation: KU Leuven
Location: Please contact Eva Lee for Zoom link

Abstract: Finding an explicit isogeny between two given isogenous elliptic curves over a finite field is considered a hard problem, even for quantum computers.