2015/11/02 by Adalto R. Gomes, Luca Amendola
Physics and Astronomy · #gr-qc #astro-ph.CO #hep-ph
paper · pdf · doi:10.1088/1475-7516/2016/02/035
28 pages. arXiv admin note: text overlap with arXiv:1306.3593
arxiv created 2015/11/02 · arxiv updated 2016/02/24
We consider the general scalar field Horndeski Lagrangian coupled to matter. Within this class of models, we present two results that are independent of the particular form of the model. First, we show that in a Friedmann-Robertson-Walker metric the Horndeski Lagrangian coincides with the pressure of the scalar field. Second, we employ the previous result to identify the most general form of the Lagrangian that allows for cosmological scaling solutions, i.e. solutions where the ratio of matter to field density and the equation of state remain constant. Scaling solutions of this kind may help solving the coincidence problem since in this case the presently observed ratio of matter to dark energy does not depend on initial conditions, but rather on the theoretical parameters.