Super-horizon second-order perturbations for cosmological random fluctuations and the Hubble-constant problem

TL;DR

This paper investigates how super-horizon second-order density perturbations can help resolve the tension between local and early-universe measurements of the Hubble constant by analyzing their non-zero spatial average.

Contribution

It introduces the role of super-horizon second-order perturbations' non-zero average in addressing the Hubble-constant discrepancy, differing from previous backreaction studies.

Findings

Super-horizon second-order perturbations have a non-zero spatial average.

These perturbations can potentially explain the Hubble-constant tension.

The approach offers a new perspective on cosmological backreaction effects.

Abstract

The super-horizon second-order density perturbations corresponding to cosmological random fluctuations are considered, their non-vanishing spatial average is shown to be useful in solving the serious problem on the cosmological tension between measured Hubble constants at present and those at the early stage, and the difference from previous works on the backreaction is discussed.