Dimensional regularization of nonlinear sigma models on a finite time   interval
  We extend dimensional regularization to the case of compact spaces. Contrary to previous regularization schemes employed for nonlinear sigma models on a finite time interval (``quantum mechanical path integrals in curved space'') dimensional regularization requires only a covariant finite two-loop counterterm. This counterterm is nonvanishing and given by R/8. 
F. Bastianelli, O. Corradini, P. van Nieuwenhuizen