Godel Universes in String Theory
  We show that homogeneous G\"odel spacetimes need not contain closed timelike curves in low-energy-effective string theories. We find exact solutions for the G\"odel metric in string theory for the full $O(\alpha ^{\prime})$ action including both dilaton and axion fields. The results are valid for bosonic, heterotic and super-strings. To first order in the inverse string tension $\alpha ^{\prime}$, these solutions display a simple relation between the angular velocity of the G\"odel universe, $\Omega ,$ and the inverse string tension of the form $\alpha ^{\prime}=1/\Omega ^2$ in the absence of the axion field. The generalization of this relationship is also found when the axion field is present. 
John D. Barrow and Mariusz P. Dabrowski