UW physicist's 'cute little calculation' may have advanced string theory

There are so many new, good ideas in string theory -- a theory proponents once touted as the key to achieving unification in physics and unlocking the remaining secrets of the universe -- that most physicists have lost hope in its promise.


		Grant M. Haller / P-I
	UW professor Andreas Karch, here teaching a class in quantum mechanics, is co-author of a paper on string theory in an American Physical Society journal.

Call it a plague of right answers. When an unproven theory produces too many right answers, scientists begin to mistrust the results.

So when Andreas Karch, a University of Washington physicist, co-wrote a proposition about the evolution of the universe in 10 dimensions, he told himself it was unlikely to be an important discovery.

But hope dies hard in a field where a unified theory is desperately wanted to explain how quarks, some of the smallest and weirdest parts of the universe, mesh with space, gravity and time as described by Einstein's theory of relativity.

That hope was described by physicist Brian Greene in his popular book "The Elegant Universe": "From one principle -- that everything at its most microscopic level consists of combinations of vibrating strands -- string theory provides a single explanatory framework capable of encompassing all forces and all matter."

If Karch is lucky, the "cute little calculation" that took several days to complete will "rescue some sort of predictive power in string theory."

Karch, 33, is a native of Germany and earned his Ph.D. at Humboldt University of Berlin. He conducted his postdoctoral work at the Massachusetts Institute of Technology and Harvard University and joined the UW in 2002. Karch wrote the article exploring the possible evolution of a 10-dimensional universe with Lisa Randall, a Harvard professor and author of the book "Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions."

Karch and Randall's paper was strong enough to garner mention in Science magazine, and Karch's work is attracting the attention of other major science forums and physicists. It was published in the October edition of a journal of the American Physical Society.

In the paper, the physicists argue that one way to reduce the number of answers spinning out of string theory is to propose a model in which the universe as we see it today was determined by a "dynamical evolution."

In their approach, Karch and Randall hypothesize an early universe that has 10 uniform dimensions filled with "branes," which are like membranes or sheets of reality, that forced the universe to expand.

Individual branes have one to 10 dimensions. In the end, those with three dimensions (such as the one we live in now) and others with seven dimensions survived the evolution. The other branes crossed and annihilated one another, as opposite electrical charges do, or expand so as to become diluted, like water spread too thin.

Even though their method won't lead to the long-sought "Unified Theory," it might turn out to be as useful as the theory of natural selection in biology, which has proved a powerful tool for understanding how species have come about and how they will continue to evolve.

The new approach would help researchers deal with all those "extra dimensions" that physicists believe are tightly wrapped up in every facet of the material world. In their theory, other three-dimensional branes, or fabrics of reality, could parallel the one in which we live, Karch said.

"But that is just as benign as saying that on some other planet, there may be people living," he said.

Their approach is a far cry from the original promise of a unified theory in physics. String theorists are still paying the price for the early declarations, Karch said.

"Nobody else has a grand unified theory, but string theorists were the ones running around saying, 'Hey! I got it! I got it!' " he said.

Karch is one of the more "levelheaded" string theorists, said Leonard Susskind, physics professor at Stanford University and a co-founder of string theory. He said Karch's three- and seven-brane work seems like a "very sensible direction" to pursue.

Randall described Karch as an expert string theorist "who cares about the real world."

Karch said he spends most of his time using the tools developed in string theory to understand the "strong force" that holds protons, neutrons and nuclei together.

But with a full teaching load, administrative duties in the physics department and a 2-year-old daughter, finding time to make his calculations is tough.

Although he uses a computer and the Internet for communication, his does his calculations on notebook paper, using a pencil.

"I try to think about how to do a calculation as hard as I can, so that when I get a chance to do the calculation, I can do it as fast as I can," he said.

Randall and Susskind say they haven't given up on the idea that string theory may yet produce results, even though they've sobered up after the heady Unified Theory days.

"If it's relevant, it's very exciting," Karch said of his recent work.

"When I was a graduate student, I decided to study string theory because of the early promises. But now, facing the reality that string theory doesn't quite do what it promised, I'm interested in what good can string theory be."

P-I reporter Jake Ellison can be reached at 206-448-8346 or jakeellison@seattlepi.com.

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