Halpern, Paul, Wesson, Paul. "4 Darkness Apparent: The Hidden Stuff of the Cosmos." Brave New Universe: Illuminating the Darkest Secrets of the Cosmos. Washington, DC: The National Academies Press, 2006.
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Brave New Universe: Illuminating the Darkest Secrets of the Cosmos
Indeed, long before the discoveries of Perlmutter, Schmidt, and their colleagues, the cosmological-constant issue was well familiar to field theorists. They came upon the problem from a different direction—their calculations produced far too high a value. Yet at the time most cosmologists assumed that lambda must be zero. How could these disparate values be reconciled? As Alan Chodos, associate executive officer of the American Physical Society, has remarked, “The old question was why is it zero? Now it is, why is it almost zero and incredibly tiny?”
This dilemma perplexed numerous researchers, such as the young Indian physicist Raman Sundrum, currently at Johns Hopkins. Sundrum carried out his Ph.D. studies of this issue under Lawrence Krauss and Mark Solvay at Case Western University well before the discovery of universal acceleration. As he recounted:
At the time there were only bounds on the acceleration, nobody had actually seen acceleration. We saw the expansion, but not the acceleration. But these bounds were already a problem in the sense that the bounds said, whatever the acceleration was it was very small, whereas theory preferred very big. And so there was already a puzzle, that got a lot more interesting when we actually saw that there was not just a bound, but actually some finite acceleration.
Sundrum delved into this riddle with gusto, trying to find an explanation in the realm of field theory. Each particle model carried with it a gumbo of masses, interaction strengths, and other parameters. By stirring these ingredients, you could try to cook up the most savory stew—matching as much as possible the flavor of observed astronomical data. In particular, you might create the magic broth that yields a delectable value of lambda. As Sundrum realized, “The cosmological constant is incredibly sensitive to microscopic physics.”
Standard field theories, however, generally serve up whopping plates of lambda, too large for general consumption. Finding these