f(R) Gravity k-Essence Late-time Phenomenology

2020/04/19 by Sergei D. Odintsov, V. K. Oikonomou, Odintsov, S. D. +3
Earth and Planetary Sciences · Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Geophysics and Gravity Measurements #High Energy Physics - Theory (hep-th) #Solar and Space Plasma Dynamics

paper · pdf · doi:10.48550/arxiv.2004.08884

openalex publication_date 2020/04/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

In this work we shall study the late-time behavior of k-Essence f(R) gravity without scalar potential, in the presence of matter and radiation perfect fluids. We quantify the late-time study by using the statefinder function Y_H(z)=\fracρ_DEρ_m⁽⁰⁾, which is a function of the redshift and of the Hubble rate. By appropriately rewriting the Friedmann equation in terms of the redshift and of the function Y_H(z), we numerically solve it using appropriate initial conditions, and we critically examine the effects of the k-Essence higher order kinetic terms. As we demonstrate, the effect of the higher order scalar field kinetic terms on the late-time dynamics is radical, since the dark energy oscillations are absent, and in addition, the cosmological physical quantities are compatible with the latest Planck data and also the model is almost indistinguishable from the Λ Cold Dark Matter model. This is in contrast to the standard f(R) gravity case, where the oscillations are present. Furthermore, by choosing a different set of values of two of the free parameters of the model, and specifically the coefficient of the higher order kinetic term and of the exponent of R^δ appearing in the f(R) action, we demonstrate that it is possible to obtain ρ_DE<0 for redshifts z∼ 2-3.8, which complies phenomenologically with, and seems to explain, the observational data for the same redshifts, and also to obtain a viable cosmological evolution at z∼ 0, at least when the dark energy equation of state parameter and the dark energy density parameters are considered.

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