Nonlinear evolution of baryon acoustic oscillations from improved perturbation theory in real and redshift spaces

We study the nonlinear evolution of baryon acoustic oscillations in the matter power spectrum and correlation function from the improved perturbation theory (PT). Based on the framework of renormalized PT, which provides a nonperturbative way to treat the gravitational clustering of large-scale structure, we apply the closure approximation that truncates the infinite series of loop contributions at one-loop order, and obtain a closed set of integral equations for power spectrum and nonlinear propagator. The resultant integral expressions are basically equivalent to those previously derived in the form of evolution equations, and they keep important nonperturbative properties which can dramatically improve the prediction of nonlinear power spectrum. Employing the Born approximation, we then derive the analytic expressions for nonlinear power spectrum and the predictions are made for nonlinear evolution of baryon acoustic oscillations in power spectrum and correlation function. We find that the improved PT possesses a better convergence property compared with standard PT calculation. A detailed comparison between improved PT results and N-body simulations shows that a percent-level agreement is achieved in a certain range in power spectrum and in a rather wider range in correlation function. Combining a model of nonlinear redshift-space distortion, we also evaluate the power spectrum and correlation function in redshift space. In contrast to the results in real space, the agreement between N-body simulations and improved PT predictions tends to be worse, and a more elaborate modeling for redshift-space distortion needs to be developed. Nevertheless, with the currently existing model, we find that the prediction of correlation function has a sufficient accuracy compared with the cosmic-variance errors for future galaxy surveys with volume of a few h(-3) Gpc(3) at z greater than or similar to 0.5.