A Locally Anisotropic Metric for Matter in an Expanding Universe: I. The Ansatz and the Modified Newton Law

TL;DR

This paper proposes a new metric ansatz that smoothly transitions between Schwarzschild and FLRW metrics, analyzing its implications for local matter and galactic dynamics, with potential relevance to dark matter phenomena.

Contribution

It introduces a novel locally anisotropic metric that interpolates between known solutions and examines its effects on Newtonian gravity at different scales.

Findings

Negligible effects on solar system dynamics.

Significant deviations at galactic scales could explain dark matter effects.

Potential to account for galaxy rotation curve flattening.

Abstract

It is suggested a metric ansatz to describe local matter in an expanding universe, hence interpolating between the Schwarzschild metric at small spatial scales and the FLRW metric at large spatial scales. This is acomplished maintaining space-time free of singularities except for the Schwarzschild mass pole at the origin as opposed to metrics already considered in the literature with the same purpose, namely the McVittie metric. The modified Newton law is analyzed and the static orbit solutions computed. It is concluded that the effects of expantion in the solar system are negligible, however depending on the metric parameter value, at galactic scales there is a significant deviation from the General Relativity Newton law which may contribute to dark matter effects allowing for a flattening of galaxy rotation curves.