Can We Understand de Sitter Spacetime with String Theory?

Abstract

Recent astronomical data point to the fact that the expanding universe is actually accelerating in expansion rate. This calls for formulating string theory in de Sitter space. There are diculties, though, since it is very dicult to formulate quantum eld theory, let alone string theory, in de Sitter space. Moreover, supersymmetry seems to be incompatible with the positive cosmological constant of de Sitter spacetime. In this paper we would like to present our work in formulating string theory in de Sitter space by utilizing bubbles of nothingness. These bubbles interpolate de Sitter space of near-bubble region and at spacetime of asymptotic region. We also comment on the resolution of the cosmological constant problem in this context.