Weak gravitational lensing in interacting dark sector models

Abstract

We explore the lines that underpin the knowledge of weak gravitational lensing, study ing basic cosmological concepts, and the construction of the matter power spectrum for ΛCDM and different scenarios. Our main goal is to investigate the possibility of interaction in the dark sector through a set of models that employ the weak lens ing formalism. This strategy proves to be promising, as the three-dimensional matter power spectrum can be directly probed with this tool. Another objective is to update the constraints on relevant cosmological parameters, including the interaction param eter of the proposed model. The spacetime is assumed to be flat and described by the Friedmann–Lemaˆıtre–Robertson–Walker metric, applied to a non-adiabatic decom posed generalized Chaplygin gas. In this framework, we recover the behavior of cold dark matter at high redshifts and of a cosmological constant in the asymptotic limit. Numerical testing is therefore crucial to evaluate the models. For this purpose, we use the CLASS Boltzmann code to simulate the interaction model, and the Cobaya sampler to compare different models, particularly with cosmic shear data from the first year of the DES-Y1 survey and with CMB data. We know that early and late-time observables do not agree with the theme of dark sector dynamics, and in this context, our investigation may contribute to assessing whether a systematic discrepancy exists between these measurements. In general, our results are consistent with the CMB data, except for the Hubble constant, H0. Our best-fit value for this parameter was lower than the standard CMB value. We find that, in the context of this dark sector study, the interaction is strongly constrained and the ΛCDM model is favored.