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July 16, 2026<br>14 min readShare

When Jacob Tsimerman was a child, his grandfather, a Russian physicist, gave him a riddle about a broken toaster. “Suppose you have three slices of bread,” his grandpa proposed, “and a toaster with two slots that toast on only one side. How many times do you need to use it to fully toast all three slices of bread?”

The first answer most people come up with – four – is also the wrong one. The correct response is three. (First, toast two slices; second, swap one out for the third slice; last, finish off the two half-toasted slices.) Tsimerman was spellbound by the solution. “I found it so beautiful and elegant,” he says. While other kids were playing with plushies and plastic trucks, he was asking his grandfather for more puzzles. “I really fell in love with it.”

By grade school, it was clear that little Jacob would become a mathematician. His mother, a high school math teacher, and father, a computer scientist, relocated the family to Toronto when he was eight, in part to grant him easier access to North America’s best schools. He started studying math at the University of Toronto at 16 and zipped through a bachelor’s degree in two years, meaning he graduated before most kids his age began orientation.

As Tsimerman climbed the academic ladder – a PhD from Princeton, a professorship back at U of T – his puzzles of choice became increasingly sophisticated. He delved into number theory, the study of integers, and algebraic geometry, a branch of math that uses geometric objects to represent solutions to polynomials. At their most complex, these disciplines are so impenetrable to laypeople that it’s practically pointless to describe them here.<br>The proof for André-Oort may not have made many headlines, but, within certain mathematical communities, the breakthrough was earth-shattering.(Chris Buck / Be Giant)What matters is that while in grad school, Tsimerman had become captivated by a number theory puzzle called the André-Oort conjecture. Higher mathematics is full of conjectures – propositions that appear to be true but lack rigorous proof – and mathematicians like Tsimerman revel in trying to prove them. André-Oort, which concerns phenomena known as special points within geometric objects called Shimura varieties, was first proposed almost 40 years ago. Many mathematicians have tried to crack it, and some have made progress, but for decades the conjecture remained stubbornly unproven.

That is until 2021, when Tsimerman and two collaborators published a paper that fully proved André-Oort. The proof may not have made many headlines, but, within certain mathematical communities, the breakthrough was earth-shattering.

It didn’t just solve one of math’s great mysteries, but also shed light on methods that other mathematicians might use to prove other conjectures. In other words, Tsimerman and his co-authors didn’t close a chapter of mathematics; they began writing a new one.

This accomplishment has positioned Tsimerman as one of the frontrunners for the Fields Medal, one of the highest honours a mathematician can earn. Often called the Nobel Prize of mathematics, the Fields is awarded to as many as four mathematicians under 40 every four years. The list of past recipients, which includes UCLA mastermind Terence Tao and the late Maryam Mirzakhani, is the closest thing math has to a hall of fame. Tsimerman will find out whether he joins those ranks when the International Mathematical Union convenes in Philadelphia in late July.

That Tsimerman is a favourite carries special weight. The Fields Medal is named after John Charles Fields, a U of T professor who promoted international co-operation among mathematicians during the interwar period, and the medal itself is struck by the Royal Canadian Mint. But the only Canadian to ever win it was Princeton professor Manjul Bhargava, who was born in Hamilton but relocated to the U.S. as a boy. Though Tsimerman was born in Russia, he would, if he wins, be the first Fields recipient to call Canada home.

The victory would also be a coup for U of T. “It’s very rare for anyone at a public university in North America to win a Fields Medal,” says Robert Jerrard, a former chair of U of T’s math department. “By the time they’re a plausible candidate, they’ve usually been vacuumed off by one of the richest universities in the world.”

Even if Tsimerman brings home the gold, most Canadians, myself included, will never understand what he does, nor what a Shimura variety is. And so I thought, to better understand Tsimerman – not how his math works, but the way his mind works – maybe I ought to start the way...