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Can Gravity and Quantum Particles Be Reconciled After All?

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Science  07 Aug 2009:
Vol. 325, Issue 5941, pp. 673
DOI: 10.1126/science.325_673

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Many theorists think it is impossible to make a quantum theory of pointlike particles—a "quantum field theory"—that also incorporates Einstein's theory of general relativity. Try it, they say, and the theory will go mathematically haywire, spitting out meaningless infinities. That supposed inevitability has been a prime motivation for string theory, which assumes that every particle is actually an infinitesimal string vibrating in nine-dimensional space—and which is inherently immune to these infinities. But point particles and gravity may be compatible after all. For several years, a group of theoretical physicists has tried to show that one particular quantum field theory of gravity known as N = 8 supergravity gives sensible answers. In a paper in press at Physical Review Letters, they take another step to show that this theory works mathematically. The work doesn't disprove string theory, but it has string theorists backpedaling a bit in their criticism of quantum field theory.