Developing a theoretical model for the resummation of infrared effects in the postreconstruction power spectrum

Since galaxy distribution reconstruction effectively reduces non-Gaussian terms in the power spectrum covariance matrix, it has attracted interest not only for baryon acoustic oscillation (BAO) signals but also for various cosmological signal analyses. To this end, this paper presents a novel theoretical model that addresses infrared (IR) effects in the postreconstruction galaxy power spectrum, including one-loop corrections. In particular, we discuss the importance of incorporating nonperturbative effects arising from IR contributions into the displacement vector s used for reconstruction. Consequently, postreconstruction nonlinear damping of BAO can be described by a single two-dimensional Gaussian function. This is a phenomenon not observed when s is considered at a linear order in the Zel'dovich approximation. Furthermore, we confirm that the cross-power spectrum of the pre- and postreconstruction density fluctuations lacks IR effect cancellations, and shows an exponential decay in both the cross-power spectrum and the associated shot-noise term.