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Friday, April 27, 2018 — 3:30 PM EDT

**Title:** Spins Lattices, Graphs and Quantum State Revivals

Speaker: | Luc Vinet |

Affiliation: | Université de Montréal |

Room: | MC 5501 |

**Abstract:**

This talk will describe how certain features of quantum transport along spin chains can be enabled.

Friday, April 20, 2018 — 3:30 PM EDT

Title: Transversals in covers of graphs

Speaker: | Krystal Guo |

Affiliation: | Université Libre de Bruxelles |

Room: | MC 5501 |

Abstract:

We study a polynomial with connections to correspondence colouring (also known as DP-colouring) and the Unique Games Conjecture.

Friday, April 13, 2018 — 3:30 PM EDT

Title: Interpolating between the characteristic and matching polynomials of a graph

Speaker: | Chris Godsil |

Affiliation: | University of Waterloo |

Room: | MC 5501 |

Abstract:

The characteristic polynomial Φ(X, t) of a graph X has two obvious combinatorial connections.

Wednesday, April 11, 2018 — 4:00 PM EDT

**Title: **Robust discrete optimization and network flows (paper by Bertsimas and Sim)

Friday, April 6, 2018 — 3:30 PM EDT

**Title:** Generating Functions: Theory, Algorithms, and Applications

Speaker: | Stephen Melczer |

Affiliation: | University of Pennsylvania |

Room: | MC 5501 |

**Abstract:**

Generating functions are an invaluable tool in many areas of discrete mathematics and beyond.

Thursday, April 5, 2018 — 1:30 PM EDT

**Title**: Graphs and Unitals

Wednesday, April 4, 2018 — 4:00 PM EDT

**Title: **Robust Solutions of Optimization Problems Affected by Uncertain Probabilities (paper by Ben-Tal A *et al* )

Tuesday, April 3, 2018 — 10:00 AM EDT

**Title:** Erdos-Hajnal meets Gyarfas-Sumner

Speaker: | Paul Seymour |

Affiliation: | Princeton |

Room: | QNC 1501 |

**Abstract:**

The Gyarfas-Sumner conjecture says that every graph with huge (enough) chromatic number and bounded clique number contains any given forest as an induced subgraph. (And non-forests do not have this property.)

Monday, April 2, 2018 — 1:00 PM EDT

**Title**: Quantum Collision-Finding in Non-Uniform Random Functions

Speaker: | Ted Eaton |

Affiliation: | ISARA Corporatio |

Room: | MC 6486 |

**Abstract: **Proving the security of a scheme against a quantum adversary often makes the strong assumption of modelling the hash function as uniformly random. In this work, we study the generic security of non-uniform random functions, specifically those with min-entropy k. This has applications to the quantum security of the Fujisaki-Okamoto transformation, as well as allowing for more relaxed security assumptions. We discuss previous results and sketch a proof for an asymptotic upper and lower bound of 2^{k/3} quantum queries.

Thursday, March 29, 2018 — 3:30 PM EDT

**Title**: Knots and their (embedded) graphs

Speaker: | Iain Moffatt |

Affiliation: | Royal Holloway University of London |

Room: | MC 5479 |

**Abstract**:

There is a classical and well-known way to describe an alternating knot or link as a plane graph, known as its Tait graph.

Wednesday, March 28, 2018 — 4:00 PM EDT

**Title**: Tractable Approximations to Robust Conic Optimization Problems (paper by D. Bertsimas, M. Sim)

Speaker: | Matthew William Slavin |

Affiliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract**: We review the paper listed in the title of this talk. In the paper, Bertsimas and Sim propose a relaxed robust counterpart for general conic optimization problems

Tuesday, March 27, 2018 — 4:00 PM EDT

**Title**: Implementing cryptography at scale

Speaker: | Edward Knapp |

Affiliation: | |

Room: | MC 5501 |

**Abstract**: Many cryptographic primitives have rough edges which make them difficult to use properly (by both experts and non-experts).

Monday, March 26, 2018 — 1:00 PM EDT

**Title**: LWE Part 2: A quantum discrete Gaussian sampler.

Speaker: | Luis Ruiz |

Affiliation: | University of Waterloo |

Room: | MC 6486 |

**Abstract:** In this talk we will describe how a (quantum) Gaussian sampler could be constructed if we had access to a solver of a decoding problem.

Friday, March 23, 2018 — 3:30 PM EDT

Title: Morphisms of complex Hadamard matrices

Speaker: | Padraig O Cathain |

Affiliation: | Worcester Polytechnic University |

Room: | MC 5501 |

Abstract:

Let M be a matrix with complex entries of unit norm. A well-known theorem of Hadamard bounds the magnitude of the determinant of M as a function of its dimension, and M is a complex Hadamard matrix if M meets Hadamard's bound with equality.

Thursday, March 22, 2018 — 3:30 PM EDT

**Title**: Excluding claws in binary matroids

Speaker: | Kazuhiro Nomoto |

Affiliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract: **A simple binary matroid is claw-free if no rank-3 flats are independent. We discuss an exact structure theorem for such matroids and sketch its proof. This is joint work with Peter Nelson.

Thursday, March 22, 2018 — 1:30 PM EDT

**Title**: Unitary groups over finite fields

Speaker: | Chris Godsil |

Affiliation: | University of Waterloo |

Room: | MC 6486 |

**Abstract**: I will discuss the unitary groups over finite fields, and the structures on which they act (these include 2-designs and generalized quadrangles).

Wednesday, March 21, 2018 — 4:00 PM EDT

**Title**: D. Bertsimas, I. Popescu - Optimal inequalities in probability theory: A convex optimization approach

Speaker: | Ashkay Ramachandran |

Affiliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract**: Abstract. We propose a semidefinite optimization approach to the problem of deriving tight moment

Friday, March 16, 2018 — 3:30 PM EDT

**Title:** A George Szekeres formula for restricted partitions

Speaker: | Bruce Richmond |

Affiliation: | University of Waterloo |

Room: | MC 5501 |

**Abstract:**

We give asymptotic formulas for the number of integer partitions of n with at most j parts and having largest part at most r, say A(n,j,r). We do this also for the number of partitions of n with largest part equal to r and having exactly j parts, say C(n,j,r).

Thursday, March 15, 2018 — 1:30 PM EDT

**Title**: Quantum State Transfer

Speaker: | Christopher van Bommel |

Affilliation: | University of Waterloo |

Room: | MC 6486 |

**Abstract**:

Many quantum algorithms may be modeled as a quantum process occurring on a graph. We interpret quantum channels implemented by spin chains as wires for transmission of states.

Wednesday, March 14, 2018 — 4:00 PM EDT

**Title: Data-driven Inverse Optimization with Imperfect Information**

Speaker: | Stefan Sremac |

Affilliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract:**

We continue our reading group with a paper by Kuhn et al with the same title as above.

Tuesday, March 13, 2018 — 4:30 PM EDT

**Title**: What's an amplituhedron?

Speaker: | Cameron Marcott |

Affilliation: | University of Waterloo |

Room: | MC 5501 |

**Abstract**:

I'll introduce the amplituhedron, focusing on why the suffix "hedron" is justified.

Monday, March 12, 2018 — 1:30 PM EDT

**Title:** LWE Part 1: The problem, the cryptosystem and its relationship to lattice Problems

Speaker: | Luiz Ruiz |

Affiliation: | University of Waterloo |

Room: | MC 6486 |

**Abstract:**

In this talk we will give an overview of the Learning With Errors problem,

Friday, March 9, 2018 — 3:30 PM EST

**Title:** Chromatic Symmetric Functions and H-Free Graphs

Speaker: | Angèle Hamel |

Affiliation: | Wilfrid Laurier University |

Room: |
MC 2038 (not 5501) |

**Abstract:**

Chromatic symmetric functions are defined in terms of colourings of particular graphs. Some key conjectures in this area concern whether chromatic symmetric functions of claw-free graphs can be written in terms of other symmetric functions with positive coefficients.

Thursday, March 8, 2018 — 3:30 PM EST

**Title:** Claws, ω and χ: induced binary submatroids

Speaker: | Peter Nelson |

Affilliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract:**

I will discuss the interplay between clique number, chromatic number, and excluding induced submatroids in the setting of binary matroids.

Thursday, March 8, 2018 — 1:30 PM EST

**Title:** Unitary Groups, II

Speaker: | Chris Godsil |

Affiliation: | University of Waterloo |

Room: | MC 6486 |

**Abstract:**

Actually the title should be 2 Unitary groups - I will discuss the 2-dimensional unitary groups.

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