Dark Energy and Modified Gravity

Abstract

Explanations of the late-time cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are mostly based on a dark energy field with fine-tuned, unnatural properties. There is a great variety of models, but all share one feature in common -- an inability to account for the gravitational properties of the vacuum energy, and a failure to solve the so-called coincidence problem. Two broad alternatives to dark energy have emerged as candidate models: these typically address only the coincidence problem and not the vacuum energy problem. The first is based on general relativity and attempts to describe the acceleration as an effect of inhomogeneity in the universe. If this alternative could be shown to work, then it would provide a dramatic resolution of the coincidence problem; however, a convincing demonstration of viability has not yet emerged. The second alternative is based on infra-red modifications to general relativity, leading to a weakening of gravity on the largest scales and thus to acceleration. Most examples investigated so far are scalar-tensor or brane-world models, and we focus on the simplest candidates of each type: $f(R)$ models and DGP models respectively. Both of these provide a new angle on the problem, but they also face serious difficulties. However, investigation of these models does lead to valuable insights into the properties of gravity and structure formation, and it also leads to new strategies for testing the validity of General Relativity itself on cosmological scales.

28 pages 11 figures

References in corpus (1)

• No-go theorem for k-essence dark energy

Cited by in corpus (31)

• CMB-S4 Science Case, Reference Design, and Project Plan
• Higher derivative theories with constraints : Exorcising Ostrogradski's Ghost
• Scaling attractors in interacting teleparallel dark energy
• Comparison of dark energy models: A perspective from the latest observational data
• Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly
• The phenomenological approach to modeling the dark energy
• Thermodynamics in $f(R)$ gravity in the Palatini formalism
• Non-adiabatic dark fluid cosmology
• Constraining $f(R)$ gravity by the Large Scale Structure
• Statefinder diagnostic and stability of modified gravity consistent with holographic and new agegraphic dark energy
• Testing Newtonian Gravity with AAOmega: Mass-To-Light Profiles and Metallicity Calibrations From 47 Tuc and M55
• Cosmology of F(T) gravity and k-essence
• A step towards testing general relativity using weak gravitational lensing and redshift surveys
• A novel teleparallel dark energy model
• Comparison of Recent SnIa datasets
• Induced cosmological constant and other features of asymmetric brane embedding
• Perturbations in electromagnetic dark energy
• Nonlinear cosmological consistency relations and effective matter stresses
• Holographic Dark Energy from a Modified GBIG Scenario
• Modified GBIG Scenario as an Alternative for Dark Energy
• Thermodynamics of Evolving Lorentzian Wormholes at Apparent Horizon in $f(R)$ Theory of Gravity
• Dynamical-Screening and the Phantom-Like Effects in a DGP-Inspired $F(R,\varphi )$ Model
• Regularization of $f(T)$ gravity theories and local Lorentz transformation
• Fractal Bubble Cosmology: A concordant cosmological model?
• A primer on problems and prospects of dark energy
• Constraining Models of Dark Energy
• Halo models in modified gravity theories with self-accelerated expansion
• Brane cosmology in the Horava-Witten heterotic M-Theory on $S^1/Z_2$
• f(R) brane cosmology
• Cosmological dynamics with modified induced gravity on the normal DGP branch
• Singularities and Soft-Big Bang in a viscous $\Lambda$CDM model