CONDENSATES AND SINGULARITIES IN STRING THEORY

We derive a class of solutions to the string sigma-model equations for the closed bosonic string. The tachyon field is taken to form a const ant condensate and the beta-function equations at one-loop level are s olved for the evolution of the metric and the dilaton. The solutions r epresent critical string theories in arbitrary dimensions. The spectru m of the subclass of models with a linearly rising asymptotic dilaton is found using the Feigin-Fuks method. Certain approximate solutions a rising in string field theory are used to illustrate the results expli citly. An argument based on conformal invariance leads to the conjectu re that stringy corrections to at least some singular spacetimes in ge neral relativity result in non-singular metrics. We use the singularit ies of the big-bang/crunch type appearing in our models to examine thi s conjecture.