The equivalence principle and the relative velocity of local inertial frames

TL;DR

This paper demonstrates that in general relativity, the relative velocity between local inertial frames is always subluminal, illustrating this principle through cosmological and black hole models.

Contribution

It explicitly proves that the relative velocity of local inertial frames in general relativity is always less than light speed, based on the equivalence principle.

Findings

Relative velocity of local inertial frames is always less than light.

Illustrations provided using FLRW and Schwarzschild models.

Abstract

In this paper we explicitly show that in general relativity, the relative velocity of two local inertial frames is always less than the velocity of light. This fact is a by-product of the equivalence principle. The general result is then illustrated within two examples, the FLRW cosmological model and the Schwarzschild metric.