Exploring the unknown: Junwu Huang illuminates dark matter

When Junwu Huang visits labs run by his experimental physicist friends, they make him wear mittens.

His friends have learned, from frustrating past incidents, that Huang is liable to curiously fiddle with sensitive equipment. So they insist his fidgety fingers stay safely corralled behind wool.

That, in part, is why Huang is a theoretical physicist instead of an experimental one.

“I wanted to be an experimentalist,” he laments, “but I’m just not good at it. I break things.”

He is exceptionally good at theoretical explorations of particle physics, however, and theoretical research allows him to conceive of ideas so novel and mind-bending that they’re still beyond the reach of laboratory experiments.

Huang, a junior faculty member at Perimeter since 2020, explores the mystery of dark matter – what it is, how to detect it, and how it interacts beyond gravity (which is currently the only indirect evidence for its existence).

“The biggest questions are about dark matter,” he says. “What is dark matter? And how can we find it? Without dark matter, the universe would look very different. Galaxies wouldn’t form the way they do.”

Huang’s research aims to narrow down the vast possibilities for what dark matter could be – ideally to give experimental colleagues precise predictions to test in the lab or seek in nature.

“As a phenomenologist, I try to figure out which dark matter models are worth pursuing and how to test them,” he explains. “Then I tell my experimentalist friends, ‘If you build this, you might find something exciting.’ Sometimes you propose an experiment, and in one or two years, they tell you if they found something. That’s exciting.”

Huang was born and raised in Hangzhou, China, a bustling city of 12 million once described by Marco Polo as “the finest and most splendid city in the world.” He developed an early aptitude for math, though he preferred applying mathematical rigour to real-world problems rather than solving problems just for the sake of it. He came to idolize Michael Faraday, the 18th century English physicist who pioneered electromagnetism. “He figured out deep physics without too much math – just experiments and intuition,” says Huang.

“I was never really interested in math,” he confides. “I didn’t want to prove things – I wanted to understand why things happen.”

As an undergrad he realized that studying physics was his best way to understand why things happen, from the tiniest subatomic interaction to the evolution of the whole cosmos. He travelled to California to earn his PhD at Stanford under the mentorship of renowned particle theorist Savas Dimopoulos, a longtime Perimeter Distinguished Visiting Research Chair. The experience was pivotal for Huang at the outset of his career.

“Savas was hands-off, but he expected quality,” Huang recalls. “He let us figure out what we really wanted to do and helped us do it.”

His Stanford experience prepared him for a postdoctoral fellowship at Perimeter Institute in 2017, and he was recruited to the Institute’s faculty three years later. He says the Institute provides him with the perfect mix of collaboration and intense solo concentration.

“Universities are great but faculty are often too busy teaching or doing other things to explore really new ideas,” he says. “Perimeter is unique because faculty have more time and space to think. That’s what I loved as a postdoc, and now I get to keep doing it.”

Occasionally, of course, his brain needs a break from all the physics. He loves to cook, which provides a kind of instant gratification that is rare in his work.

“With cooking, in 20 minutes you know if you made something good or bad,” he says, “unlike physics, where answers can take years.”

The puzzle of dark matter is one such problem that could be many years away from a solution – or a breakthrough could be just around the corner. The uncertainty is part of the excitement for Huang.

"I hope in my career we will understand what dark matter is made of,” he says. “And I hope we do it here."