Generalized $f(R,\varphi ,X)$ gravity and the late-time cosmic acceleration

Abstract

High-precision observational data have confirmed with startling evidence that the Universe is currently undergoing a phase of accelerated expansion. This phase, one of the most important and challenging current problems in cosmology, represents a new imbalance in the governing gravitational equations. Historically, physics has addressed such imbalances by either identifying sources that were previously unaccounted for, or by altering the gravitational theory. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity models, amongst others. Outstanding questions are related to the nature of this so-called "dark energy" that is driving this acceleration, and whether it is due to the vacuum energy or a dynamical field. On the other hand, the late-time cosmic acceleration may be due to modifications of General Relativity. In this work we explore a generalised modified gravity theory, namely $f(R,\varphi ,X)$ gravity, where $R$ is the Ricci scalar, $\varphi$ is a scalar field, and $X$ is a kinetic term. This theory contains a wide range of dark energy and modified gravity models. We considered specific models and applications to the late-time cosmic acceleration.

13 pages, 1 figure; slightly revised version, displayed name corrected. arXiv admin note: text overlap with arXiv:1412.0867

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• Exploring Axial Symmetry in Modified Teleparallel Gravity
• Constraining the Schwarzschild-de Sitter Solution in Models of Modified Gravity
• Observational Tests of Gauss-Bonnet Like Dark Energy Model
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• Anisotropic Spheres Via Embedding Approach in $f(R,\varphi ,X)$ Gravity
• Solar system tests for realistic $f(T)$ models with nonminimal torsion-matter coupling
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• Unified dynamical system formulations for $f(R,\varphi ,X)$ gravity with applications to nonminimal derivative coupling and $R^2$-Higgs inflation