2017/07/31 by Cristiano Germani, Prado Martin-Moruno · 1 citation
Physics and Astronomy · #gr-qc #astro-ph.CO #hep-ph #hep-th
published as Physics of the Dark Universe 18C (2017) pp. 1-5 · 14 pages, v2: comment on frames added. Conclusions unchanged, version accepted for publication in Physics of the Dark Universe
arxiv created 2017/09/05 · arxiv updated 2017/09/26
Assuming both that our Universe is evolving into a de Sitter space and a vanishing cosmological constant, leaves only the option that the observed acceleration is provided by a "kinetic" energy of a scalar field. From an effective field theory point of view, the absence of Ostrogradsky instabilities restricts the choice to shift-symmetric Horndeski theories. Within these theories, we find the conditions for the existence of a de Sitter critical point in a universe filled by matter, radiation and a Horndeski scalar. Moreover, we show that this point is a universal attractor and we provide the tracking trajectory. Therefore, if a de Sitter fixed point exists within these models, our Universe will eventually evolve into a de Sitter space. As an example, we have discussed the case of the combined Galileon-Slotheon system, in which the Galileon is kinetically non-minimal coupled to the Einstein tensor. Interestingly, we have also found that the tracker trajectory of this system does not follow previous literature assumptions.