The Consistent Newtonian Limit of Einstein's Gravity with a Cosmological Constant

TL;DR

This paper derives the exact Newtonian limit of Einstein's gravity with a positive cosmological constant, revealing a finite valid range for Newtonian physics and a maximum mass, contrasting with the zero cosmological constant case.

Contribution

It provides the first derivation of the Newtonian limit of Einstein's gravity including a positive cosmological constant, highlighting new constraints and boundary conditions.

Findings

Existence of a maximum range for Newtonian approximation.

Presence of a maximum mass ${\\cal M}_{max}(\Lambda)$.

Boundary conditions must be set at finite range, not infinity.

Abstract

We derive the `exact' Newtonian limit of general relativity with a positive cosmological constant $\Lambda$. We point out that in contrast to the case with $\Lambda = 0 $, the presence of a positive $\Lambda$ in Einsteins's equations enforces, via the condition $| \Phi | \ll 1$, on the potential $\Phi$, a range ${\cal R}_{max}(\Lambda) \gg r \gg {\cal R}_{min} (\Lambda)$, within which the Newtonian limit is valid. It also leads to the existence of a maximum mass, ${\cal M}_{max}(\Lambda)$. As a consequence we cannot put the boundary condition for the solution of the Poisson equation at infinity. A boundary condition suitably chosen now at a finite range will then get reflected in the solution of $\Phi$ provided the mass distribution is not spherically symmetric.