COSMOLOGICAL QUANTUM STRING VACUA AND STRING-STRING DUALITY

Implications of string-string dualities to cosmological string vacua a re discussed. Cosmological vacua of classical string theories comprise of disjoint classes mapped one another by scale-factor T-duality. Eac h classes are, however, afflicted with initial/final cosmological sing ularities. It is argued that quantum string theories and string-string dualities dramatically resolve these cosmological singularities out s o that disjoint classical cosmological vacua are continuously connecte d in a unified manner. A natural inflationary cosmology follows from t his.