Superstrings in ten dimensions are not by themselves the truly fundamental objects that physicists once thought them to be. Strings alone cannot be fundamental because two of the five superstring theories are dual to an 11-dimensional theory, yet perturbative string theories cannot be defined consistently in 11 dimensions. A truly fundamental nonperturbative theory must contain a range of basic objects in addition to strings. In fact, in order to be consistent, a fundamental theory — which we may as well call M-theory — must contain a range of objects called p-branes. These are non-perturbative objects, which do not correspond to the oscillations states of a string. Indeed, it was partly by examining the properties of branes that physicists were led to the notion of M-theory. The purpose of this chapter is to describe the notion of branes in a little more detail — and to describe one of the great triumphs of M-theory to date: a better understanding of black holes.
KeywordsBlack Hole Event Horizon Heterotic String Black Hole Entropy Topological Defect
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