The dark side of gravity: Modified theories of gravity

Abstract

Modern astrophysical and cosmological models are faced with two severe theoretical difficulties, that can be summarized as the dark energy and the dark matter problems. Relative to the former, it has been stated that cosmology has entered a 'golden age', in which high-precision observational data have confirmed with startling evidence that the Universe is undergoing a phase of accelerated expansion. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity, amongst others. One is liable to ask: What is the so-called 'dark energy' that is driving the acceleration of the universe? Is it a vacuum energy or a dynamical field (''quintessence'')? Or is the acceleration due to infra-red modifications of Einstein's theory of General Relativity? In the context of dark matter, two observations, namely, the behavior of the galactic rotation curves and the mass discrepancy in galactic clusters, suggest the existence of a (non or weakly interacting) form of dark matter at galactic and extra-galactic scales. It has also been proposed that modified gravity can explain the galactic dynamics without the need of introducing dark matter. We briefly review some of the modified theories of gravity that address these two intriguing and exciting problems facing modern physics.

17 pages, invited chapter to appear in an edited collection 'Dark Energy-Current Advances and Ideas'

Cited by in corpus (78)

• f(R,T) gravity
• Testing General Relativity in Cosmology
• $f(Q,T)$ gravity
• Coupling matter in modified $Q$-gravity
• Further matters in space-time geometry: $f(R,T,R_{\mu \nu }{T}^{\mu \nu })$ gravity
• $f(T,\mathcal{T})$ gravity and cosmology
• Generalized curvature-matter couplings in modified gravity
• Hybrid metric-Palatini gravity
• An Alternative f (R, T) Gravity Theory and the Dark Energy Problem
• Structure of neutron, quark and exotic stars in Eddington-inspired Born-Infeld gravity
• Extended $f(R,L_m)$ gravity with generalized scalar field and kinetic term dependences
• Matter Bounce Loop Quantum Cosmology from $F(R)$ Gravity
• Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly
• Geodesic deviation, Raychaudhuri equation, and tidal forces in modified gravity with an arbitrary curvature-matter coupling
• Thermodynamics in $f(R)$ gravity in the Palatini formalism
• Constraining $f(R)$ gravity by the Large Scale Structure
• Beyond Einstein's General Relativity: Hybrid metric-Palatini gravity and curvature-matter couplings
• Global Monopole in Palatini f(R) gravity
• On the non-attractive character of gravity in f(R) theories
• FRW Cosmology in $f(Q,T)$ Gravity
• Various Hamiltonian formulations of f(R) gravity and their canonical relationships
• Cosmology in scalar-tensor $f(R,T)$ gravity
• Non-minimal Maxwell-Modified Gauss-Bonnet Cosmologies: Inflation and Dark Energy
• Noether Symmetry Approach for teleparallel-curvature cosmology
• The Raychaudhuri equation in homogeneous cosmologies
• Cosmic acceleration and crossing of $\omega =-1$ in non-minimal modified Gauss-Bonnet gravity
• Spherically symmetric static vacuum solutions in hybrid metric-Palatini gravity
• Dynamic wormhole geometries in hybrid metric-Palatini gravity
• Interior Solutions of Fluid Sphere in f(R,T) Gravity Admitting Conformal Killing Vectors
• Bayesian evidence for $\alpha$-attractor dark energy models
• The Reconstruction of Constant Jerk Parameter with $f(R,T)$ Gravity
• Interacting Dark Energy in Hořava-Lifshitz Cosmology
• Thick brane structures in generalized hybrid metric-Palatini gravity
• Cosmological models in $f(T,\mathcal{T})$ gravity and the dynamical system analysis
• Reconstruction of an Observationally Constrained $f(R,T)$ gravity model
• String Inspired Quintom Model with Non-minimally Coupled Modified Gravity
• General constraints on Horndeski wormhole throats
• Crossing of Phantom Divide in $F(R)$ Gravity
• Late-time cosmological evolution of a general class of f(R, T) gravity with minimal curvature-matter coupling
• Cosmography and large scale structure by f(R) gravity: new results
• Cosmological dynamics of interacting dark energy and dark matter in viable models of f(R) gravity
• Cosmological anisotropy from non-comoving dark matter and dark energy
• Thermodynamics of Evolving Lorentzian Wormholes at Apparent Horizon in $f(R)$ Theory of Gravity
• $f(Q,L_m)$ gravity, and its cosmological implications
• Cosmic stringlike objects in hybrid metric-Palatini gravity
• Weak-field regime of the generalized hybrid metric-Palatini gravity
• Can cosmic acceleration be caused by exotic massless particles?
• Light deflection and gravitational lensing effects inspired by loop quantum gravity
• The virial theorem in Eddington-Born-Infeld gravity
• Finite-time singularities in modified $\mathcal{F}(R,G)$-gravity and singularity avoidance
• Cosmological Boundary Flux Parameter
• Neutron Stars In $f(R,T)$ Theory: Slow Rotation Approximation
• Early and Late-time Cosmic Acceleration in Non-minimal Yang-Mills-$f(G)$ Gravity
• Dynamics of Magnetized Bulk Viscous Strings in Brans-Dicke Gravity
• $\kappa (R,T)$ gravity
• Effective $f(R)$ actions for modified Loop Quantum Cosmologies via order reduction
• Hybrid f(R) theories, local constraints, and cosmic speedup
• Effective Actions for Loop Quantum Cosmology in Fourth-Order Gravity
• Reconstruction of DBI-essence dark energy with f(R) gravity and its effect on black hole and wormhole mass accretion
• Why the mean anomaly at epoch is not used in tests of non-Newtonian gravity?
• Modified Theories of Gravity: Traversable Wormholes
• A note on wormholes in slightly modified gravitational theories
• Cosmography in F(G) modified gravity
• Extended f(R,L_m) theories of gravity
• Cosmological Models in Modified f(R) Gravity Theories
• Behavior of $F(R)$ gravity around a crossing of the phantom divide
• Modified $f(R)$ Gravity and Thermodynamics of Time-Dependent Wormholes at Event Horizon
• Generalized Einstein-Maxwell field equations in the Palatini formalism
• Nonrelativistic Dark-Energy Fluid in a Baby Universe
• Connecting noncommutative geometry to f(R) modified gravity
• Analytic solution of the algebraic equation associated to the Ricci tensor in extended Palatini gravity
• Energy Conditions in a Generalized Second-Order Scalar-Tensor Gravity
• Comparing $f(R)$ modified gravity and noncommutative geometry in the context of dark matter and traversable wormholes: a survey
• Towards degeneracy problem breaking by large scale structures methods
• Static spherically symmetric black holes in de Rham-Gabadadze-Tolley massive gravity in arbitrary dimensions
• Matter growth in extended $\Lambda$CDM cosmology
• Cosmology in the novel scalar-tensor representation of $f(R,T)$ gravity
• Gravastars in a Non-minimally Coupled Gravity with Electromagnetism