Dark Energy: the equation of state description versus scalar-tensor or modified gravity

TL;DR

This paper compares different mathematical frameworks—fluid equations, scalar-tensor theories, and modified gravity—for describing dark energy, providing a method to distinguish among them using observational data.

Contribution

It presents an explicit technique to transform between equation of state descriptions and scalar-tensor or modified gravity models, aiding in identifying the true physical description of dark energy.

Findings

Equivalent descriptions can be matched to observational data.

The technique enables discrimination between different theoretical models.

Frameworks can be transformed explicitly between each other.

Abstract

Dark energy dynamics of the universe can be achieved by equivalent mathematical descriptions taking into account generalized fluid equations of state in General Relativity, scalar-tensor theories or modified F(R) gravity in Einstein or Jordan frames. The corresponding technique transforming equation of state description to scalar-tensor or modified gravity is explicitly presented. We show that such equivalent pictures can be discriminated by matching solutions with data capable of selecting the true physical frame.