O (d)⊗O (d) Symmetry of the space of cosmological solutions in string theory, scale factor duality, and two-dimensional black holes

Abstract

It is shown that there is an O (d)⊗O (d) transformation that, acting on a cosmological type (time dependent but space translation invariant) solution of the (d+1)-dimensional string field theory, generates new cosmological solutions. The solutions related by these transformations describe physically different space-time in general, except for the diagonal O(d) subgroup which generates rotation. This is an extension of the leading order result of Meissner and Veneziano to all orders in the inverse string tension α'. In 1+1 dimension the relevant group is Z₂⊗Z₂, and we discuss the effect of these transformations on the recently discovered black hole solution.