Phase-space analysis of dark energy models in non-minimally coupled theories of gravity
Youri Carloni, Orlando Luongo
Abstract
Abstract We analyze scalar field dark energy models minimally and non-minimally coupled to gravity, postulating that a Yukawa-like interacting term is in form equivalent for general relativity, teleparallel and symmetric-teleparallel theories. Our analysis is pursued within two scalar field representations, where a quintessence and phantom pictures are associated with quasiquintessence and quasiphantom exotic fields. In the latter, we suggest how the phion-pressure can be built up without exhibiting a direct kinetic term. Accordingly, the stability analysis reveals that this quasiquintessence field provides a viable description of the Universe indicating, when minimally coupled, how to unify dark energy and dark matter by showing an attractor point where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>w</mml:mi> <mml:mrow> <mml:mi>ϕ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:math> . Conversely, in the non-minimally coupling, the alternative field only leaves an attractor where dark energy dominates, mimicking de facto a cosmological constant behavior. A direct study is conducted comparing the standard case with the alternative one, overall concluding that the behavior of quintessence is well established across all the gravity scenarios. However, considering the phantom field non-minimal coupled to gravity, the results are inconclusive for power-law potentials in Einstein theory, and for the inverse square power potential in both teleparallel and symmetric-teleparallel theories. Finally, we study the growth of matter perturbations and establish that only the fifth power and quadratic potentials, when used to describe quasiphantom field minimally coupled to gravity, exhibit behavior similar to the ΛCDM model.