﻿ UNH professor solves ancient mathematics riddle | New Hampshire
All Sections

# UNH professor solves ancient mathematics riddle

By PAUL FEELY

June 02. 2013 12:25AM

Yitang Zhang has set the math world abuzz by solving a problem posed centuries ago. (Courtesy)

It sounds like a feel-good Hollywood hit. A virtual unknown comes out of nowhere to pull off an upset, achieving success where many have failed.

Who knows whether a mathematical breakthrough would equal box-office millions, but among those who crunch numbers for a career, Yitang Zhang has gone from relatively obscure to rock star status in four weeks, after word spread that he had taken a step toward solving one of the world's oldest mathematical problems.

Zhang, or "Tom" as he is known around the campus of the University of New Hampshire, where he works as a lecturer and professor of undergraduate calculus, formulated a proof that takes aim at a problem first posed by Euclid. The "twin prime conjecture" states that there are an infinite number of prime numbers that are only two numbers apart, like 3 and 5 or 17 and 19.

Primes are numbers that can't be divided evenly by any other whole number - they are divisible only by 1 and themselves.

Zhang said mathematicians like himself consider prime numbers to be the basis of all mathematics, similar to the periodic table in chemistry.

Zhang's work, which has been described as proving a weak version of the twin prime conjecture, demonstrated that the number of prime pairs that are less than 70 million units apart is infinite.

"The prime numbers are, by definition, very simple. But there are very deep mysteries about them, and been very difficult to prove this result," said Zhang, a lecturer in the department of mathematics for almost a decade.

Zhang's proof has attracted attention since word was leaked on May 9 that the editors at a respected journal, Annals of Mathematics, accepted his paper on the proof.

"The jump from 2 to 70 million is nothing compared to the jump from 70 million to infinity," states an article in the journal Nature.

Mathematicians interviewed in several publications about Zhang's work have used terms like "beautiful," "stunned," and "astounded" when discussing the proof.

Zhang said had been thinking about the twin prime conjecture for three years with no success. He said the proof came to him while he was visiting a friend in Colorado on vacation.

He credits his success to never giving up on a problem, as a matter of personal pride.

"The idea is based on an accumulation of my thinking for several years," said Zhang. "I had tried various methods. To answer why others could not get it and I could, I may say that I had been working harder and never gave up."

Zhang said that because his wife has a job in California, and the couple has no children, he has devoted a lot of time to thinking about prime numbers. Eventually, he said, his mind worked through the problem.

"I was also lucky, perhaps," he added. "I didn't bring any notes, any books, any paper, and suddenly it came to me."

After receiving word his paper had been accepted, Zhang was invited to give a lecture on his work at Harvard University.

The talk drew more than 50 people, a large crowd for a virtual unknown in the mathematics community.

Zhang said that, in the days since, he has received dozens of emails and requests to talk about his breakthrough. He said his new 'celebrity' status has been a bit "unnerving."

"I'm used to being a shy person," said Zhang. "The reactions are much more than I had expected. The requests, the emails...these are not what I want. I wish it would be over soon, so that I could return to my previous situation."

He acknowledges that the proof has no practical application in the real world.

"There is really only interest from people in this field," said Zhang.