Cosmography: Cosmology without the Einstein equations

TL;DR

This paper explores how cosmography, based on symmetry principles, can analyze the universe's features independently of Einstein's equations, reducing reliance on complex dark energy and matter models.

Contribution

It demonstrates that cosmography can effectively describe the universe's kinematics without depending on Einstein's equations or detailed stress-energy content.

Findings

Cosmography allows analysis of the Hubble law without Einstein equations.

Symmetry principles enable model-independent cosmological insights.

Cosmography reduces reliance on dark energy and matter assumptions.

Abstract

How much of modern cosmology is really cosmography? How much of modern cosmology is independent of the Einstein equations? (Independent of the Friedmann equations?) These questions are becoming increasingly germane -- as the models cosmologists use for the stress-energy content of the universe become increasingly baroque, it behoves us to step back a little and carefully disentangle cosmological kinematics from cosmological dynamics. The use of basic symmetry principles (such as the cosmological principle) permits us to do a considerable amount, without ever having to address the vexatious issues of just how much "dark energy", "dark matter", "quintessence", and/or "phantom matter" is needed in order to satisfy the Einstein equations. This is the sub-sector of cosmology that Weinberg refers to as "cosmography", and in this article I will explore the extent to which cosmography is sufficient for analyzing the Hubble law and so describing many of the features of the universe around us.