Emergence of classical space-time from the Planck era

The origin of the Friedmann space-time is discussed in the context of the heterotic superstring theory, with simultaneous reference to the structure and symmetries of the internal space, taking into account the a causality of the Planck era. It is also shown how the overall form of the higher-derivative terms R2=B̃(R2−RijRij) in the low-energy effective Lagrangian, previously calculated exactly from the vanishing of the four-loop beta function of the two-dimensional, world-sheet sigma model due to Freeman et al., can be obtained by perturbative application of the zero-action hypothesis, assuming the Zelʹdovich equation of state p=ρ in the limit as the initial singularity is approached in time reversal.