Loose Strings: Pressure mounts to tie string theory to the real world

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By Roger Snodgrass

The Nobel Laureate in Physics introduced his mind-boggling subject in a way that cats and dogs could understand, with a cartoon from the New Yorker.

A middle-aged urban couple are walking down the street and the woman says to the man, "It's all string theory to me."

David Gross, Director of the Kavli Institute for Theoretical Physics at Santa Barbara, California proceeded to deliver a progress report on string theory that returned the favor by sounding at times very much like Greek.

This week of advanced science talks at the lab culminated in a lecture by Gross who offered a note of apology about the string theory of reality, to which he has been a major contributor

"It hasn't led to any big observational payoffs," he said.

Among other essential ideas, string theory posits that "at the bottom of it all," all matter and all forces including gravity are made up of extended strings vibrating at different frequencies in multiple dimensions of space and one dimension of time.

In 2004, Gross shared the Nobel Prize in Physics with Frank Wilczek his graduate student at Harvard, and with David Politzer, who was working on the problem separately at Princeton. The prize recognized their theoretical work explaining how elementary constituents in an atomic nucleus are bound together to form protons and neutrons.

They discovered a phenomenon called "Asymptotic Freedom," which means the nuclear force operating between the elementary constituents of matter known as quarks was, contrary to common sense, weaker rather than stronger the closer they were together.

That put into place "the final block of the standard model," said LANL Fellow Rajan Gupta in introducing Gross Thursday.

Gross talked mainly about the achievements of string theory, a vast and complicated "theory of everything" that has absorbed him and whole departments of the physics and mathematics community for several decades. He summarized the current state of elementary particle physics, but his thoughts were also aimed over the horizon at what he called "the coming revolution in fundamental physics."

String theory has provided fascinating insights into how Einstein's Theory of General Relativity, dealing with the nature of space and time, can be squared with quantum mechanics, which has successfully characterized the "standard model" of elementary particles and explained the interactions between and among different kinds of energy and matter.

In May, the Large Hadron Collider (LHC) operated by the European Organization for Nuclear Research (CERN), will begin circulating its two accelerated beams, the most powerful in the world, expected to harvest new particles from colliding protons traveling at nearly the speed of light.

The outcome may add or subtract from the accumulated intellectual capital invested in string theory and other attempts at a "grand unified theory" to resolve gaps and contradictions in how physics describes the universe, including "dark matter" and "dark energy."

Located on the border of France and Switzerland, the LHC's headline tasks include the potential discovery of a Higgs boson, a relatively massive particle known as "the god particle," that would help explain how other particles have mass. Proof of its existence would tend to support string theory, according to the theorists.

A member of LANL's Theoretical Division, astrophysicist Salman Habib said after the talk that string theory remains difficult to assess.

"It's a funny field to look at from the outside because it has yet to connect with the outside world," he said. "Mathematically, it's very pretty and theorists like to do fundamental mathematical computations, but they have not led to any big observational payoffs so far.

String theory has been given a great deal of popular exposure in recent years by Brian Greene of Columbia University. His nonfiction book "The Elegant Universe" was nominated for a Pulitzer Prize and was later made into a PBS television series narrated by the author.

More recently, grousing among anti-string theorists has become louder, signified by such books as "The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next," by Les Smollin, a theoretician at Canada's Perimeter Institute in Waterloo, Ontario, and "Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law," by Peter Woit of Columbia University.

These books responded to what both authors considered aggressive promotion and mutual loyalties of string-theorists and criticized what many researchers have seen as excessive time in the limelight considering the modest gains.

Gross said, "We are still not sure what string theory is."

While discussing an anticipated revolution, he also weighed potential "problems with the revolution."

"String theory has had many successes," he said, "but the best is yet to come."