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Thursday, June 18, 2020 2:30 pm - 2:30 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Victor Reiner

Title: Sandpiles and representation theory

Speaker: Victor Reiner
Affiliation: University of Minnesota
Zoom: Contact Karen Yeats

Abstract:

For an undirected graph, its sandpile group is an interesting isomorphism invariant-- it is a finite abelian group that describes the integer cokernel of the graph's Laplacian matrix.

Friday, June 19, 2020 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Nicolas Trotignon

Title: Widths in even-hole-free graphs

Speaker: Nicolas Trotignon
Affiliation: CNRS - LIP - École Normale Supérieure de Lyon
Zoom: Please email Emma Watson

Abstract:

Historically, the study of even-hole-free graphs is motivated by the analogy with perfect graphs. The decomposition theorems that are known for even-hole-free graphs are seemingly more powerful than the ones for perfect graphs: the basic classes and the decompositions are in some respect more restricted. But strangely, in an algorithmic perpective, much more is known for perfect graphs. 

Thursday, June 25, 2020 2:30 pm - 2:30 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Ali Mahmoud

Title: 2-Connected Chord Diagrams and Applications in QFT

Speaker: Ali Mahmoud
Affiliation: University of Waterloo
Zoom: Contact Karen Yeats

Abstract:

A functional equation for 2-connected chord diagrams is derived, then is used to calculate asymptotic information for the number of 2-connected chord diagrams by means of alien derivatives applied to factorially divergent power series.

Thursday, July 2, 2020 2:30 pm - 2:30 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Timothy Miller

Title: Factorial Schur Functions and Quantum Intergrability

Speaker: Timothy Miller
Affiliation: University of Waterloo
Zoom: Contact Karen Yeats

Abstract:

I will introduce factorial Schur functions as they relate to my Master's thesis. Factorial Shur functions are a generalization of Schur functions with a second family of "shift" parameters. In 2009, Zinn-Justin reproved the answer to a tiling problem (the puzzle rule) with a toy fermionic model, using techniques from physics to extract the result.

Friday, July 3, 2020 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Peter Selinger

Title: Number-theoretic methods in quantum computing

Speaker: Peter Selinger
Affiliation: Dalhousie University
Zoom: Please email Emma Watson

Abstract:

An important problem in quantum computing is the so-called \emph{approximate synthesis problem}: to find a quantum circuit, preferably as short as possible, that approximates a given target operation up to given $\epsilon$. For nearly two decades, from 1995 to 2012, the standard solution to this problem was the Solovay-Kitaev algorithm, which is based on geometric ideas. This algorithm produces circuits of size $O(\log^c(1/\epsilon))$, where $c$ is a constant approximately equal to $3.97$. It was a long-standing open problem whether the exponent $c$ could be reduced to $1$.

Monday, July 6, 2020 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory seminar - Maxwell Levit

Title: A covering graph perspective on Huang’s theorem 

Speaker: Maxwell Levit
Affiliation: University of Waterloo
Zoom: Contact Soffia Arnadottir

Abstract:

Just about a year ago, Hao Huang resolved the sensitivity conjecture by proving that any induced subgraph on more than half the vertices of the hypercube $Q_n$ has maximum degree at least $\sqrt(n)$. The key ingredient in his proof is a special $\pm 1$ signing of the adjacency matrix of $Q_n$.

Thursday, July 9, 2020 2:30 pm - 2:30 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Olya Mandelshtam

Title: Formulas for Macdonald polynomials arising from the ASEP

Speaker: Olya Mandelshtam
Affiliation: Brown University
Zoom: Contact Karen Yeats

Abstract:

The asymmetric simple exclusion process (ASEP) is a one-dimensional model of hopping particles that has been extensively studied in statistical mechanics, probability, and combinatorics. It also has remarkable connections with orthogonal symmetric polynomials in many variables such as Macdonald and Koornwinder polynomials.

Friday, July 10, 2020 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Felix Leditzky

Title: Symmetries and asymptotics of port-based teleportation

Speaker: Felix Leditzky
Affiliation: University of Waterloo
Zoom: Please email Emma Watson

Abstract:

Quantum teleportation is one of the fundamental building blocks of quantum Shannon theory. The original teleportation protocol is an exact protocol and amazingly simple, but it requires a non-trivial correction operation to make it work. Port-based teleportation (PBT) is an approximate variant of teleportation with a simple correction operation that renders the protocol unitarily covariant.

Monday, July 13, 2020 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory Seminar - Sebastian Cioaba

Title: On the flip graph on perfect matchings of complete graphs and sign reversal graphs

Speaker: Sebastian Cioaba
Affiliation: University of Delaware
Zoom: Contact Soffia Arnadottir

Abstract:

In this talk, we study the flip graph on the perfect matchings of a complete graph of even order. We investigate its combinatorial and spectral properties including connections to the signed reversal graph and we improve a previous upper bound on its chromatic number.

Thursday, July 16, 2020 2:30 pm - 2:30 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Oliver Pechenik

Title: Dynamics of plane partitions

Speaker: Oliver Pechenik
Affiliation: University of Waterloo
Zoom: Contact Karen Yeats

Abstract:

Consider a plane partition P in an a X b X c box. The rowmotion operator sends P to the plane partition generated by the minimal elements of its complement. We show rowmotion resonates with frequency a+b+c-1, in the sense that each orbit size shares a prime divisor with a+b+c-1. This confirms a 1995 conjecture of Peter Cameron and Dmitri Fon-Der-Flaass. (Based on joint works with Kevin Dilks & Jessica Striker and with Becky Patrias.)