After 38 Years, Israeli Solves Math Code

JERUSALEM (AP) -- A mathematical puzzle that baffled the top minds in the esoteric field of symbolic dynamics for nearly four decades has been cracked - by a 63-year-old immigrant who once had to work as a security guard.

Avraham Trahtman, a mathematician who also toiled as a laborer after moving to Israel from Russia, succeeded where dozens failed, solving the elusive "Road Coloring Problem."

The conjecture essentially assumed it's possible to create a "universal map" that can direct people to arrive at a certain destination, at the same time, regardless of starting point. Experts say the proposition could have real-life applications in mapping and computer science.

The "Road Coloring Problem" was first posed in 1970 by Benjamin Weiss, an Israeli-American mathematician, and a colleague, Roy Adler, who worked at IBM at the time.

For eight years, Weiss tried to prove his theory. Over the next 30 years, some 100 other scientists attempted as well. All failed, until Trahtman came along and, in eight short pages, jotted the solution down in pencil last year.

"The solution is not that complicated. It's hard, but it is not that complicated," Trahtman said in heavily accented Hebrew. "Some people think they need to be complicated. I think they need to be nice and simple."

Weiss said it gave him great joy to see someone solve his problem.

Stuart Margolis, a mathematician who recruited Trahtman to teach at Bar Ilan University near Tel Aviv, called the solution one of the "beautiful results." But he said what makes the result especially remarkable is Trahtman's age and background.

"Math is usually a younger person's game, like music and the arts," Margolis said. "Usually you do your better work in your mid 20s and early 30s. He certainly came up with a good one at age 63."

Adding to the excitement is Trahtman's personal triumph in finally finding work as a mathematician after immigrating from Russia. "The first time I met him he was wearing a night watchman's uniform," Margolis said.

Originally from Yekaterinburg, Russia, Trahtman was an accomplished mathematician when he came to Israel in 1992, at age 48. But like many immigrants in the wave that followed the breakup of the Soviet Union, he struggled to find work in the Jewish state and was forced into stints working maintenance and security before landing a teaching position at Bar Ilan in 1995.

The soft-spoken Trahtman declined to talk about his odyssey, calling that the "old days." He said he felt "lucky" to be recognized for his solution, and played down the achievement as a "matter for mathematicians," saying it hasn't changed him a bit.

The puzzle tackled by Trahtman wasn't the longest-standing open problem to be solved recently. In 1994, British mathematician Andrew Wiles solved Fermat's last theorem, which had been open for more than 300 years.

Trahtman's solution is available on the Internet and is to be published soon in the Israel Journal of Mathematics.

Joel Friedman, a math professor at the University of British Columbia, said probably everyone in the field of symbolic dynamics had tried to solve the problem at some point, including himself. He said people in the related disciplines of graph theory, discrete math and theoretical computer science also tried.

"The solution to this problem has definitely generated excitement in the mathematical community," he said in an e-mail.

Margolis said the solution could have many applications.

"Say you've lost an e-mail and you want to get it back - it would be guaranteed," he said. "Let's say you are lost in a town you have never been in before and you have to get to a friend's house and there are no street signs - the directions will work no matter what."

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On the Net:

Trahtman's solution: http://arxiv.org/abs/0709.0099

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