@article { , title = {Parametrized post-Friedmannian framework for interacting dark energy theories}, abstract = {We present the most general parametrization of models of dark energy in the form of a scalar field which is explicitly coupled to dark matter. We follow and extend the parametrized 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 nonzero coefficients. This paves the way for a model-independent approach to classify and test interacting dark energy theories.}, doi = {10.1103/PhysRevD.91.083537}, eissn = {1550-2368}, issn = {2470-0010}, issue = {8}, journal = {Physical Review D}, publicationstatus = {Published}, publisher = {American Physical Society}, url = {https://nottingham-repository.worktribe.com/output/749081}, volume = {91}, year = {2015}, author = {Skordis, C. and Pourtsidou, A. and Copeland, Edmund J.} }