Sensitivity of Cosmological Parameter Estimation to Nonlinear Prescription from Cosmic Shear

Several ongoing and upcoming large scale structure surveys aim to explore the nonlinear regime of structure formation with high precision. Making reliable cosmological inferences from these observations necessitates precise theoretical modeling of the mildly nonlinear regime. In this work we explore how the choice of nonlinear prescription would impact parameter estimation from cosmic shear measurements for a Euclid-like survey. Specifically, we employ two different nonlinear prescriptions of Haloft and the Effective Field Theory of the Large Scale Structure and compare their measurements for the three different cosmological scenarios of $\Lambda$CDM, $w$CDM and $(w_0,w_a)$CDM. We also investigate the impact of different nonlinear cutoff schemes on parameter estimation. We find that the predicted errors on most parameters shrink considerably as smaller scales are included in the analysis, with the amount depending on the nonlinear prescription and the cutoff scheme used. We use predictions from the Halofit model to analyze the mock data from DarkSky $N$-body simulations and quantify the parameter bias introduced in the measurements due to the choice of nonlinear prescription. We observe that $\sigma_8$ and $n_{\rm{s}}$ have the largest measurement bias induced by inaccuracies of the Halofit model.