Relic Gravitational Waves and the Evolution of the Universe
  In the inflation models, the relic gravitational waves (RGW) generated in the inflation stage, and evolved in the Universe until now. In the different cosmological evolution models, one can get different gravitational waves power spectrum. In this paper, we give a simple formula to estimate this spectrum in a general cosmological model. From this formula, one can easily find the relation between this power spectrum and the cosmological evolution models. The spectrum includes all the information about the evolution of the scale factor $a$ from inflation to now.   So RGW is a more clear fossil, which records the cosmological evolution information, and be a useful complementarity for another fossil$-$Cosmic   Microwave Background Radiation (CMB). 
Wen Zhao