NONLINEAR BEHAVIOR OF BARYON ACOUSTIC OSCILLATIONS FROM THE ZEL'DOVICH APPROXIMATION USING A NON-FOURIER PERTURBATION APPROACH

Baryon acoustic oscillations are an excellent technique to constrain the properties of dark energy in the universe. In order to accurately characterize the dark energy equation of state, we must understand the effects of both the nonlinearities and redshift space distortions on the location and shape of the acoustic peak. In this paper, we consider these effects using the Zel'dovich approximation and a novel approach to second-order perturbation theory. The second-order term of the Zel'dovich power spectrum is built from convolutions of the linear power spectrum with polynomial kernels in Fourier space, suggesting that the corresponding term of the Zel'dovich correlation function can be written as a sum of quadratic products of a broader class of correlation functions, expressed through simple spherical Bessel transforms of the linear power spectrum. We show how to systematically perform such a computation. We explicitly prove that our result is the Fourier transform of the Zel'dovich power spectrum and compare our expressions to numerical simulations. Finally, we highlight the advantages of writing the nonlinear expansion in configuration space, as this calculation is easily extended to redshift space, and the higher-order terms are mathematically simpler than their Fourier counterparts.