Backreaction in cosmic screening approach

TL;DR

This paper examines the impact of nonlinear perturbations on the universe's evolution using the cosmic screening approach, finding that second-order effects are negligible and do not significantly alter the Friedmann equations.

Contribution

It provides an analytical and numerical analysis confirming that second-order scalar perturbations have minimal backreaction effects in the cosmic screening framework.

Findings

Second-order perturbations have negligible backreaction on the Friedmann equations.

The second-order correction to the gravitational potential is much smaller than the first-order.

The perturbation expansion in the cosmic screening approach is validated.

Abstract

We investigate the backreaction of nonlinear perturbations on the global evolution of the Universe within the cosmic screening approach. To this end, we have considered the second-order scalar perturbations. An analytical study of these perturbations followed by a numerical evaluation shows that, first, the corresponding average values have a negligible backreaction effect on the Friedmann equations and, second, the second-order correction to the gravitational potential is much less than the first-order quantity. Consequently, the expansion of perturbations into orders of smallness in the cosmic screening approach is correct.