Distance-redshift from an optical metric that includes absorption

TL;DR

This paper extends the optical metric framework to include absorption effects, deriving a new distance-redshift relation that can explain supernova observations without dark energy.

Contribution

It introduces a modified optical metric incorporating absorption, enabling a geometric interpretation of light attenuation in cosmology.

Findings

Derived a new distance-redshift relation including absorption effects.

Fitted supernova data with the model, offering an alternative to dark energy.

Showed absorption can mimic cosmic acceleration in observational data.

Abstract

We show that it is possible to equate the intensity reduction of a light wave caused by weak absorption with a geometrical reduction in intensity caused by a "transverse" conformal transformation of the spacetime metric in which the wave travels. We are consequently able to modify Gordon's optical metric to account for electromagnetic properties of ponderable material whose properties include both refraction and absorption. Unlike refraction alone however, including absorption requires a modification of the optical metric that depends on the eikonal of the wave itself. We derive the distance-redshift relation from the modified optical metric for Friedman-Lema\^itre-Robertson-Walker spacetimes whose cosmic fluid has associated refraction and absorption coefficients. We then fit the current supernovae data and provide an alternate explanation (other than dark energy) of the apparent acceleration of the universe.