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Holography in string theory DeBoer, Philip Albert

Abstract

This thesis presents three aspects of holography, or holographic duality, in string theory. The goal of holography is to describe gravitational theories by field theories in fewer dimensions. Although recently there have been significant strides toward understanding generic holographic dualities between particle theory and gravity, it is not clear how string theory might implement this. In Chapter 2 the role of compact directions in holography is explored. We discover that a generalization of Bousso's prescription is necessary. In this chapter we also discover that holography provides no clear solution to understanding closed timelike curves, unlike earlier speculation. Using holography as a tool, we are able in Chapter 3 to compute the thermal two-point function of the graviton in the dual to a Little String Theory. This is a strongly coupled non-gravitational theory. It exists as a limit of a certain weakly coupled string theory. We find a typical thermal spectrum with no obvious interpretation in terms of particles and bound states. We find evidence supporting a conjecture that this theory is thermodynamically unstable. Finally, in Chapter 4, we investigate the inhomogeneous decay of an unstable D-brane. We study the average number and energy of closed strings emitted during the decay, and confirm that the space-filling D-brane decays completely into lower-dimensional D-branes. One of the long-term goals of this research is to understand how closed-string fluctuations appear in the open-string sector of string theory. This is directly related to the appearance of holography in string theory since gravity appears in the closed-string sector, while the end-points of open strings can be described by field theory.

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