The Parameterized Post-Friedmannian Framework for Interacting Dark Energy Theories

TL;DR

This paper extends the Parameterized Post-Friedmannian framework to include interacting dark energy models, providing a systematic, model-independent way to classify and constrain these theories using a reduced parameter space.

Contribution

It introduces a generalized parametrization for scalar field dark energy models coupled to dark matter, expanding the PPF approach to encompass interactions.

Findings

Framework successfully reduces free parameters for dark energy models.

Demonstrates applicability through worked examples.

Enables model-independent classification of interacting dark energy theories.

Abstract

We present the most general parametrisation of models of dark energy in the form of a scalar field which is explicitly coupled to dark matter. We follow and extend the Parameterized Post-Friedmannian approach, previously applied to modified gravity theories, in order to include interacting dark energy. We demonstrate its use through a number of worked examples and show how the initially large parameter space of free functions can be significantly reduced and constrained to include only a few non-zero coefficients. This paves the way for a model-independent approach to classify and test interacting dark energy theories.