From Subway sandwich maker to mathematical star: The improbable ascent of Yitang Zhang

Follow the journey of Yitang Zhang, the mathematician who solved the bounded gaps problem after years of working at Subway, now a professor in China.

By: AXL Media

Published: Apr 11, 2026, 8:02 AM EDT

Source: Information for this report was sourced from VnExpress.

A Late Arrival to the Mathematical Pantheon

The landscape of modern mathematics was fundamentally altered in April 2013 when an obscure adjunct professor from the University of New Hampshire submitted a paper to the Annals of Mathematics. Yitang Zhang, then 55 years old, presented a solution to the "Bounded Gaps Between Primes" problem, demonstrating that infinitely many pairs of prime numbers exist with a gap of less than 70 million. The peer review process, which typically spans months or years, was completed in just three weeks as experts confirmed that Zhang had established a landmark theorem. According to Peter Sarnak, a professor at the Institute for Advanced Study, the result was spectacular because Zhang was an unknown figure who had previously produced very little visible work.

The Invisible Years of a Subway Scholar

Before his academic breakthrough, Zhang’s professional life was defined by extreme hardship and academic exile. After earning his PhD from Purdue University in 1991, he was unable to secure a research position, a struggle he attributed to a lack of recommendation letters from his adviser and a quiet personality that hindered professional networking. For seven years, he survived through a series of odd jobs that included delivering food and working at a Subway sandwich shop, where he managed bookkeeping and prepared orders. During this era of obscurity, Zhang occasionally slept in his car, yet he maintained his research in isolation. He later remarked that he did not give up because he felt mathematical research was a pursuit that could be conducted anywhere.

A Moment of Clarity in Colorado

The conceptual breakthrough that would eventually end Zhang’s anonymity occurred on July 3, 2012, during a walk near a friend's residence in Colorado. After three years of stagnant progress on the bounded gap problem, he suddenly identified a viable path forward. He dedicated the following eight months to refining his proof and two additional months to independent review, as he knew no one capable of vetting the complex logic. Upon the acceptance of his paper, Zhang was catapulted into a world of international lectures and prestigious awards, though he expressed a preference for a quiet and peaceful life. Colleagues like Matthew Emerton of the University of Chicago noted that despite his sudden fame, Zhang remained remarkably humble and unaffecte...