Effect of a possible cosmological time dependence of the gravitational parameter G on the peak luminosity of type Ia supernovae

TL;DR

This paper investigates whether a cosmological variation in the gravitational constant G could influence the peak luminosity of type Ia supernovae, concluding that G remains effectively constant locally and does not affect supernova brightness.

Contribution

The study demonstrates that local measurements of G are unaffected by cosmic expansion, confirming the stability of type Ia supernovae as standard candles across cosmic time.

Findings

G is practically unaffected by cosmic expansion at local scales

Type Ia supernova luminosity remains unchanged over cosmic time

Local gravitational physics is stable despite universe's expansion

Abstract

The cosmological expansion of the universe affects the behaviour of all physical systems and, in the case of gravitationally bound ones, could correspond to or mimic a time dependent Newton's constant. Here we discuss the case of a locally spherical mass distribution embedded in a generic Robertson Walker universe. Choosing the most appropriate metric tensor for the problem and assuming that the local time scale is much much lower than the cosmic one, we show that G is practically unaffected thus leaving the absolute magnitude of type Ia supernovae unaltered at all epochs.