Prime number breakthrough by unknown professor

A virtually unknown professor has taken a major step towards solving a numerical problem which has baffled the finest minds in mathematics for centuries.

Dr Yitang Zhang is a researcher at the University of New Hampshire Photo: UNH

By Nick Collins, Science Correspondent

Dr Yitang Zhang, who once resorted to working at Subway when he could not find an academic job, has received glowing reviews for his "astounding" new paper on number theory.

His breakthrough is a significant step towards proving a long-standing theory on prime numbers – numbers which can only be divided by themselves and by one.

The development is all the more astonishing because Dr Zhang, a researcher at the University of New Hampshire, had until now been a virtual unknown even among experts in his field.

A quirk of prime numbers is that they often come in pairs separated by two, which are known as "twin primes", for example three and five, 11 and 13 or 18383549 and 18383551.

Prime numbers are common at the lower end of the numerical scale and become much rarer among larger numbers, but although twin primes become extremely hard to find there is no suggestion they vanish completely.

Mathematicians have long theorised that there is an infinite number of twin primes – an idea known as the "twin prime conjecture" – but none have ever been able to prove it.

Dr Zhang took a major step towards doing so, however, by demonstrating that no matter how large a twin prime is, there will always be another pair of primes separated from it by less than 70 million.

Although his paper does not conclusively show that there is an infinite number of twin primes, it effectively proves that the gaps between prime pairs does not keep on growing to an infinite size.

Richard Taylor, a member of the editorial board at the Annals of Mathematics journal, where the paper was published, said Dr Zhang had published "hardly anything" before and was not regarded as a "big name".

"It's a steady stream of papers which tends to get you jobs," he added. "Maybe he likes to think about the big problems – and you don't solve those very often".

Dr Zhang told The Independent the 70 million figure in his paper could in fact be reduced to a smaller number, but he may leave that work to someone else and "turn my interest to some other problems".

He added that working at Subway while searching for a job at a university "wasn't bad" but that "whenever I was doing it I was thinking about maths".