Reconstructing the primordial spectrum of fluctuations of the universe from the observed nonlinear clustering of galaxies

We have discovered that the nonlinear evolution of the two point correlation function in N-body experiments of galaxy clustering with OMEGA = 1 appears to be described to good approximation by a simple general formula. The underlying form of the formula is physically motivated, but its detailed representation is obtained empirically by fitting to N-body experiments. We present here this formula, along with an inverse formula which converts a final, nonlinear correlation function into the initial, linear correlation function. We apply the inverse formula to observational data from the CfA, IRAS, and APM galaxy surveys, and hence reconstruct the initial spectrum of fluctuations of the universe, if OMEGA = 1.