Time Gauge Fixing and Hilbert Space in Quantum String Cosmology
  Recently the low-energy effective string theory has been used by Gasperini and Veneziano to elaborate a very interesting scenario for the early history of the universe (``birth of the universe as quantum scattering''). Here we investigate the gauge fixing and the problem of the definition of a global time parameter for this model, and we obtain the positive norm Hilbert space of states. 
Marco Cavaglia` and Vittorio de Alfaro