Spacelike Singularities and String Theory

An interpretation of spacelike singularities in string theory uses target space duality to relate the collapsing Schwarzschild geometry near the singularity to an inflationary cosmology in dual variables. An appealing picture thus results whereby gravitational collapse seeds the formation of a new universe. PACS numbers: 04.70.-s, 11.25.-w String theory is strongly believed to solve the short-distance problems of quantum gravity by providing a fundamental length scale lstr = √ h̄c/T , where T is the string tension. Perturbative studies of high-energy string scattering (Gross and Mende 1988, Amati et.al. 1988), the stringy resolution of orbifold singularities (Dixon et.al. 1985), and target-space duality (for a review, see Giveon et.al. 1994) all point in this direction. Thus one might expect that there is no such thing as a ‘naked’ or timelike singularity in string theory; the exponentially soft high energy behavior of the theory (in weak coupling, at least) will forbid any observation of the kinds of arbitrarily violent processes associated with high field gradients over small regions. The decay of strong electromagnetic fields by string pair production (Bachas and Porrati 1992; see also Fradkin and Tseytlin 1985, Russo and Tseytlin 1994) also supports this picture of the string’s aversion to large field strengths. Spacelike singularities, such as those encountered in black hole formation, seem to mount a stronger challenge. In this case, the singularity is in the future; all the soft high-energy behavior is helpless in the face of the crushing together of future-directed light cones inside the black hole horizon. No causal force can prevent collapse; indeed the soft high-energy behavior of strings at high energy would seem to act in the wrong direction, placing an upper limit on any potential stabilizing force. How then can string theory be a complete theory of nature if it does not tell us