Wednesday, June 11, 2025

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• Running the numbers for the Faculty of Mathematics convocation ceremony
• Sepehr Assadi and international collaborators receive STOC 2025 Best Paper Award
• Engineering mourns the passing of Elder Bill Woodworth

Running the numbers for the Faculty of Mathematics convocation ceremonies

Convocation continues today with three ceremonies for the Faculty of Mathematics. In case you're wondering why there are three ceremonies, here are the numbers: 1,682 undergraduates, 173 Master's, and 42 PhD candidates will cross the stage today. That's 1,897 degrees, diplomas and certificates in total.

Morning ceremony

The morning ceremony will take place at 10:00 a.m. Watch the livestream.

Julie-Anne Desrochers will sing the national anthem.

Carrying the mace will be Dr. Changbao Wu.

Dr. Gordon Willmot will be named Distinguished Professor Emeritus. Dr. Willmot was Professor of Actuarial Science in the Department of Statistics and Actuarial Science at the University of Waterloo from 1986 to 2024. He was the inaugural Munich Re Chair in Insurance from 2001 to 2021. Professor Willmot is an outstanding mathematician known for his foundational contributions to insurance risk modelling and ruin theory. He has published over 100 research papers and co-authored 5 books. He is among the most-cited actuarial scholar of all time. His stellar contributions to graduate supervision led him to be the recipient of a prestigious Award of Excellence in Graduate Supervision in 2022.

Dr. Mary Hardy will be named Distinguished Professor Emerita. Dr. Mary Hardy is a transformative figure in actuarial science and quantitative finance. Over her 26-year tenure in the Department of Statistics and Actuarial Science, Dr. Hardy established herself as an internationally renowned scholar, educator, and leader. A visionary researcher in actuarial science and risk management, Dr. Hardy's pioneering research bridged theoretical advancements with practical challenges in insurance and pensions. Her work on investment guarantees and risk management drove regulatory changes that fortified Canadian insurers during the 2007–2009 financial crisis. She is the former Editor-in-Chief of the North American Actuarial Journal and Annals of Actuarial Science. As the founding director of Waterloo’s Master of Actuarial Science program, she established a rigorous, intense, and rewarding pathway for aspiring actuaries. In honour of her legacy, a scholarship in her name was created to support students who are committed to serving the public good.

Keeley Isinghood will deliver the valedictory address.

Afternoon ceremony

The afternoon ceremony begins at 2:30 p.m. Watch the livestream.

Julie-Anne Desrochers will sing the national anthem.

Dr. Martin Karsten will carry the mace.

Nina Tan will deliver the valedictory address.

Evening ceremony

The evening ceremony begins at 7:00 p.m. Watch the livestream.

Michael Klein will sing the national anthem.

Judith Ann Koeller will carry the mace.

Karen Abdel Sater will deliver the valedictory address.

Outstanding students receiving major medals and awards include:

Sepehr Hajebi will be named University Finalist for the Governor General's Gold Medal at the Doctoral level. Sepehr graduated in fall 2024.

Laura Pierson will receive the Governor General's Academic Gold Medal for highest standing in a Master's program. Pierson graduated in fall 2024.

Yu Li will receive the Governor General's Academic Silver Medal for highest standing in an undergraduate degree program. Li graduated in fall 2024.

Zev Max Friedman will receive the University of Waterloo Alumni Gold Medal for outstanding academic achievement.

 Sepehr Assadi and international collaborators receive STOC 2025 Best Paper Award

Sepehr Assadi is an Associate Professor and a Faculty of Mathematics Research Chair at the Cheriton School of Computer Science.

This article originally appeared on the Cheriton School of Computer Science website.

Professor Sepehr Assadi and his international collaborators — Soheil Behnezhad, Sayan Bhattacharya, Martín Costa, Shay Solomon and Tianyi Zhang — have received a Best Paper Award at STOC 2025, the 57^th ACM Symposium on Theory of Computing.

Held annually since 1969, STOC covers all areas of research within algorithms and complexity theory and is one of the two most prestigious conferences in theoretical computer science. The award recognizes the research team’s paper, Vizing’s Theorem in Near-Linear Time, which introduces a randomized algorithm that computes a (∆ + 1)-edge colouring in near-linear time with high probability, a near-optimal result for this classic problem in graph theory. 

“STOC Best Paper Awards are an exceptional recognition for research that is both novel and significant in the field of theoretical computer science,” said Raouf Boutaba, University Professor and Director of the Cheriton School of Computer Science. “Sepehr and his colleagues have achieved an outstanding result, showing that edge colouring — a foundational problem in graph theory — can be solved efficiently in near-linear time.”

Understanding Vizing’s theorem

Imagine a network of cities connected by roads. In graph theory, each city is a vertex, and each road an edge. The challenge is to assign a colour to each road so that no two roads meeting at the same city share the same colour. Additionally, we would like to use the smallest possible number of colours for this task.

Suppose the busiest city (vertex) in the network has Δ roads (edges) connected to it. Or, in more technical terms, let Δ denote the maximum degree of the graph. It is easy to see that at the very least we need Δ colours for colouring the network to ensure that no two roads incident on the busiest city have the same colours. It is also easy to see that in general, we may not always be able to colour the network with precisely Δ colours: consider a trio of cities all connected to each other via direct roads — one clearly cannot colour all roads in this network with only two colours and ensure no two roads meeting at the same city share the same colour, even though Δ = 2 in this network.

So then, what’s the minimum number of colours required to colour every graph?

This question is effectively answered by Vizing’s theorem, a foundational result in graph theory formulated by mathematician Vadim Vizing in 1964. Vizing’s theorem states that any graph can have its edges coloured using at most Δ + 1 colours — that is with just one more colour than its maximum degree. In other words, Δ colours are always necessary in any graph and Vizing’s theorem states Δ + 1 colours are also always sufficient. By now, Vizing’s theorem has been recognized as a fundamental theorem in graph theory and appears in most textbooks or courses in this area.

But, in addition to knowing every graph can be coloured Δ + 1 colours, we are also interested in designing algorithms that can find such a colouring of every given graph as fast as possible. This is the topic of a long line of research in algorithm design.

About this award-winning research

Vizing’s original proof also implies an algorithm for finding an edge colouring with Δ + 1 colours in O(mn) time — here, m is the number of edges in the graph and n is the number of vertices (this algorithm is described in detail in articles by Rao and Dijkstra, and by Misra and Gries, both from 1992). Later refinements improved this to (nearly) O(m√n) time, independently discovered by Eshrat Arjomandi in 1982 and by Harold Gabow, Takao Nishizeki, Oded Kariv, Daneil Leven and Osamu Terada in 1985. (These algorithms were further simplified and analyzed more carefully by Corwin Sinammon in 2019.)

The O(m√n) runtime for this problem remained a longstanding barrier for nearly four decades until very recently. In 2024, independently and concurrently, using randomization, this runtime bound was further improved to Õ(n²) by Sepehr Assadi and to Õ(mn^1/3) by Sayan Bhattacharya, Din Carmon, Martín Costa, Shay Solomon and Tianyi Zhang. Even more recently and subsequent to these developments, the latter algorithm was further improved to Õ(mn^1/4) time by Sayan Bhattacharya, Martín Costa, Shay Solomon and Tianyi Zhang in 2025.

The team’s STOC 2025 award-winning paper now effectively concludes this long line of research. They present a randomized algorithm that computes a (∆ + 1)-edge colouring in only O(m log ∆) time, with high probability. Modulo a small factor of log ∆, which is almost negligible in this context, this runtime is now as fast as simply reading the entire input once! This development represents a near-optimal solution for this fundamental problem in graph theory.

Engineering mourns the passing of Elder Bill Woodworth

This article was originally published on the Faculty of Engineering website.

Elder William (Bill) Woodworth, who played a vital role in advancing Indigenous presence and perspective at the University of Waterloo, passed away unexpectedly June 9, 2025.

A long-time faculty member in the School of Architecture and Elder in Residence for the Faculty of Engineering, Woodworth supported students, faculty and staff by sharing his knowledge, stories and care for community. His calm presence brought people together, encouraged meaningful conversations and helped make the University a more welcoming and respectful place for everyone.

Woodworth (Raweno;kwa in his Haudenosaunee name) was a member of the Lower Mohawk Kanien'kehá:ka Nation of Six Nations of the Grand River in the Bear Clan. He worked tirelessly to build bridges between Indigenous and non-Indigenous communities and to shape a campus culture grounded in respect, listening and humility.

“His presence reminded us all of the importance of listening and learning with humility,” said Dean Mary Wells in a message to the Faculty. “His passing is a profound loss.”

Details about opportunities to honour Elder Bill’s memory will be shared with the University of Waterloo community as they become available.