  Implications of string-string dualities to cosmological string vacua are
discussed. Cosmological vacua of classical string theories comprise of disjoint
classses mapped one another by scale-factor T-duality. Each classes are,
however, afflicted with initial/final cosmological singularities. It is argued
that quantum string theories and string-string dualities dramatically resolve
these cosmological singularities out so that disjoint classical cosmological
vacua are continuously connected in a unified manner. A natural inflationary
cosmology follows from this.

High Energy Physics - Theory