The C&O department has 36 faculty members and 60 graduate students. We are intensely research oriented and hold a strong international reputation in each of our six major areas:
- Algebraic combinatorics
- Combinatorial optimization
- Continuous optimization
- Cryptography
- Graph theory
- Quantum computing
Read more about the department's research to learn of our contributions to the world of mathematics!
News
Three C&O faculty win Outstanding Performance Awards
The awards are given each year to faculty members across the University of Waterloo who demonstrate excellence in teaching and research.
Sina Kalantarzadeh wins Governor General's Gold Medal
The Governor General’s Gold Medal is one of the highest student honours awarded by the University of Waterloo.
Two C&O faculty win Outstanding Performance Awards
The awards are given each year to faculty members across the University of Waterloo who demonstrate excellence in teaching and research.
Events
Crypto Reading Group on quantum computing | Masuda Fatima & Maggie Simmons, Quantum Key Distribution
| Speaker: | Masuda Fatima & Maggie Simmons |
| Affiliation: | University of Waterloo |
| Room: | MC 5501 |
Abstract: Quantum Key Distribution (QKD) uses the laws of Quantum Mechanics to allow two parties to produce a shared secret key only known to them without it's security relying on the computational hardness. In this presentation, we will introduce the QKD protocol BB84, and present how it is secure against various attacks. We will also discuss two major phases in BB84: the information reconciliation phase between keys of sender and receiver via error correcting codes and the privacy amplification phase where two communicating parties distill highly secret shared key from a larger body of a shared key, which is only partially secret. Finally, we will give a brief overview of Muckle-based hybrid authenticated key exchange (AKE) protocols.
Algebraic and Enumerative Combinatorics Seminar | Patty Commins, Signed combinatorics and the Mantaci–Reutenauer algebra
| Speaker: | Patty Commins |
| Affiliation: | Laboratoire d'Algèbre, de Combinatoire et d'Informatique Mathématique (LACIM) |
| Location: | MC 5417 |
Abstract: The Mantaci–Reutenauer algebra is a subalgebra of the group algebra of signed permutations which has close ties to symmetric functions, descents, and characters. In this talk, we explore its representation theory and explain how it is governed by simple operations on signed versions of classical combinatorial objects (i.e. partitions, necklaces). This builds on a well-studied type A story for Solomon's "descent algebra". The representation-theoretic data we will consider include the Cartan matrix, the representation type, and a conjectural Ext-quiver; we will explain these notions during the talk. This is ongoing joint work with Alice Dell'Arciprete.
There will be a pre-seminar presenting relevant background at the beginning graduate level starting at 1:30pm in MC 5417.
Tutte Colloquium | Sepehr Assadi, Greedy is Optimal for the Semi-Streaming Matching Problem
| Speaker: | Sepehr Assadi |
| Affiliation: | University of Waterloo |
| Location: | MC 5501 |
Abstract: We prove that no single-pass semi-streaming algorithm (deterministic or randomized) can achieve a better-than-half approximation to the maximum matching problem. This implies the optimality of the naive greedy algorithm, answering a longstanding open question in graph streaming literature since the introduction of the model. Our proof consists of two main parts:
1. Blueprint framework: reducing the problem of proving lower bounds for semi-streaming matching to constructing certain combinatorial objects which we call blueprints; and,
2. Blueprint construction: an optimal construction of such blueprints usable within this framework.
Putting these two parts together implies our semi-streaming matching lower bound.
Based on joint work with Max Jiang and Mars Xiang in https://arxiv.org/abs/2607.14644 (STOC 2026) and https://arxiv.org/abs/2607.14656 (arXiv; July 2026)