# On Backreaction in Newtonian cosmology

## TL;DR

This paper clarifies the known theorem that there is no global kinematical backreaction in Newtonian cosmology, addressing recent claims and misinterpretations by other researchers.

## Contribution

It clarifies the existing theorem on backreaction in Newtonian cosmology and critiques recent claims of its violation.

## Key findings

- Reaffirms the theorem of no global backreaction in Newtonian cosmology
- Critiques incomplete restatements and claims of recent papers
- Clarifies the scope and limitations of the theorem

## Abstract

We clarify that a result recently stated by Kaiser is contained in a theorem of Buchert and Ehlers that is widely known for its main result: that there is no global kinematical backreaction in Newtonian cosmology. Kaiser cites this paper, re-derives parts of the theorem, but incompletely restates its content. He makes further claims, which cannot be proven beyond the limited context of Newtonian cosmology. We also discuss recent papers of R\'acz et al. and Roukema who claim the existence of global backreaction within the Newtonian framework.