Strings and Quantum Gravity








Ever since the discovery of quantum mechanics, a tremendous amount of energy has been spent by physicists, including Einstein himself, in an effort to reconcile the theory of general relativity, which describes gravity, and quantum mechanics, which seems to describe everything else. For some odd reason, no quantum mechanical phenomena associated with gravity were ever observed, nor could anyone come up with a quantum theory of gravity. All other forces in Nature have been proven to have a quantum origin. If we claim that the Universe is quantum in nature, then surely gravity cannot be excluded.

About thirty years ago, we witnessed the birth of string theory, which together with supersymmetry, managed to offer a unified quantum description of Nature, including the gravitational force. Alas, it was so complicated, that it was almost impossible to extract any useful information that could be tested in experiments. Despite its shortcomings, it remained a very useful theoretical laboratory to test ideas that could shed light on the fundamental structure of Nature. Recently, we saw an explosion of such ideas, connecting seemingly unrelated objects and pointing to an underlying principle yet to be discovered. Specifically, for the first time, the origin of thermodynamic properties of black holes were understood microscopically. This pointed to a solution of the "information loss paradox" (nothing can escape from a black hole except thermal radiation, discovered by Hawking). The present situation bears a lot of similarities with the confusion at the turn of the century regarding the electromagnetic properties of light and the constancy of its speed. Einstein solved that puzzle by introducing his Principle of Equivalence and the Theory of Relativity. It is such an underlying principle that we seem to be missing today.

Led by Dr. Siopsis, the HET group's efforts are directed at contributing to these developments by carving through the complexities of (super)string theory to study the properties of black holes, including thermodynamics, quantization issues and scattering. The group is funded by the Department of Energy under grant No. DE-FG05-91ER40627.


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