On The Interpolating Solutions of Strings in Different Backgrounds
  We analyze the beta-function equations for string theory in the case when the target space has one spacelike (or timelike) direction and rest is some conformal field theory (CFT) with appropriate central charge and has one nearly marginal operator. We show there always exists a space (time) dependent solution which interpolates between the original background and the background where CFT is replaced by a new conformal field theory, obtained by perturbing CFT by the nearly marginal operator. 
Sudipta Mukherji