Effective Field Theories for Dark Energy

Recent attempts have been made to derive the most general effective theory of dark energy involving gravity and a scalar field, including up to four derivatives of the fields. The resulting effective field theory incorporates a number of different models, including quintessence, k-essence, and ghost condensation. However, the derivation of these effective theories neglect issues related to the choice of frame and the coupling between the scalar field and gravity. Taking these issues into consideration, we propose a slightly different construction for and discuss the implications of the resulting effective theory.