Modified gravity and cosmology

Clifton, Timothy; Ferreira, Pedro G.; Padilla, Antonio; Skordis, Constantinos

doi:10.1016/j.physrep.2012.01.001

Cited by 3,864 publications

(3,992 citation statements)

References 1,166 publications

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“…Notice more generally that neither K nor G (1) contribute to g ζ and c ζ : thus in the G-inflation limit we also have g ζ = c ζ = 1. On the other hand G (2) and G (3) contribute to all four expressions.…”

Section: Scalar Perturbationsmentioning

confidence: 94%

“…However, since for certain applications of our analysis we may wish to set L (2) = 0 (see (1.3)-(1.5)), we keep the Einstein-Hilbert term explicit. Whilst the Lagrangian L (0) and L (1) are familiar from k and G-inflation, terms L (2,3) represent completely new class of scalar field theories which has not been explored so far. In L (3) ,…”

Section: Generalized Galileons: Field Equationsmentioning

confidence: 99%

“…The expressions for ρ (1) , P (1) and q (1) can straightforwardly be read off from (2.8) from which it follows that π (1) µν = 0. For T (2,3) µν the situation is yet more complicated, and from (2.9) and (B.1) they both lead to non-vanishing anisotropic stress π (2,3) µν as well as energy flow.…”

Section: (N)mentioning

confidence: 99%

“…Furthermore, since α, β are constraints, their first order solution α (1) and β (1) are adequate for our purpose to evaluate the power spectrum and bispectrum.…”

Section: Linear Perturbationsmentioning

confidence: 99%

“…Recently a great deal of effort has been devoted to developing consistent modified gravity theories which, as an alternative to to dark energy or the cosmological constant, may provide an explanation of cosmic acceleration (for a recent review, see [1]). Such IR modification of gravity arise, for example, in higher-dimensional setups as in the DGP model where self-acceleration is sourced by a scalar field φ, the helicity-0 mode of the 5D graviton.…”

Section: Introductionmentioning

confidence: 99%

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Inflation and primordial non-Gaussianities of “generalized Galileons”

Gao

Steer

2011

J. Cosmol. Astropart. Phys.

126

141

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Abstract. We set up cosmological perturbation theory and study the cosmological implications of the so-called "generalized Galileon" developed in [6, 7]. This is the most general scalar field theory whose Lagrangian contains derivatives up to second order while keeping second order equations of motion, and contains as sub-cases k-inflation, G-inflation and many other models. We calculate the power spectrum of the primordial curvature perturbation, finding a modification of the usual consistency relation of the tensor-to-scalar ratio in k-inflation or perfect fluid models. Finally we also calculate the bispectrum, which contains no new shapes beyond those of k-inflation.

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Section: Scalar Perturbationsmentioning

confidence: 94%

Section: Generalized Galileons: Field Equationsmentioning

confidence: 99%

Section: (N)mentioning

confidence: 99%

“…Furthermore, since α, β are constraints, their first order solution α (1) and β (1) are adequate for our purpose to evaluate the power spectrum and bispectrum.…”

Section: Linear Perturbationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inflation and primordial non-Gaussianities of “generalized Galileons”

Gao

Steer

2011

J. Cosmol. Astropart. Phys.

126

141

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Model‐independent constraints on r^‐3 extra‐interactions from orbital motions

Iorio

2012

Annalen der Physik

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Constraints on long-range power-law modifications Upert ∝ r −3 of the usual Newtonian gravitational potential UN ∝ r −1 are inferred from orbital motions of well known artificial and natural bodies. They can be interpreted in terms of a characteristic length ℓ which may be identified with, e.g., the anti-de Sitter (AdS) radius of curvature ℓ in the Randall-Sundrum (RS) braneworld model, although this not a mandatory choice. Our bounds, complementary to those from tabletop laboratory experiments, do not rely upon more or less speculative and untested theoretical assumptions, contrary to other long-range RS tests proposed in astrophysical scenarios in which many of the phenomena adopted may depend on the system's composition, formation and dynamical history as well. Independently of the interpretation of ℓ, the perihelion precession of Mercury and its radiotechnical ranging from the Earth yield ℓ 10 − 50 km. Tighter bounds come from the perigee precession of the Moon, from which it can be inferred ℓ 500 − 700 m. The best constraints (ℓ 5 m) come from the Satellite-to-Satellite Tracking (SST) range of the GRACE A/B spacecrafts orbiting the Earth: proposed follow-on of such a mission, implying a sub-nm s −1 range-rate accuracy, may constrain ℓ at ∼ 10 cm level. Weaker constraints come from the double pulsar system (ℓ 80 − 100 km) and from the main sequence star S2 orbiting the compact object in Sgr A * (ℓ 6.2 − 8.8 AU). Such bounds on the length ℓ, which must not necessarily be identified with the AdS radius of curvature of the RS model, naturally translate into constraints on an, e.g., universal coupling parameter K of the r −3 interaction. GRACE yields K ≤ 1 × 10 16 m 5 s −2 .

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Material models of dark energy

Pearson

2014

Annalen der Physik

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We review and develop a new class of "dark energy" models, in which the relativistic theory of solids is used to construct material models of dark energy. These are models which include the effects of a continuous medium with well defined physical properties at the level of linearized perturbations. The formalism is constructed for a medium with arbitrary symmetry, and then specialised to isotropic media (which will be the case of interest for the majority of cosmological applications). We develop the theory of relativistic isotropic viscoelastic media whilst keeping in mind that we ultimately want to observationally constrain the allowed properties of the material model. We do this by obtaining the viscoelastic equations of state for perturbations (the entropy and anisotropic stress), as well as identifying the consistent corner of the theory which has constant equation of state parameterẇ = 0. We also connect to the non-relativistic theory of solids, by identifying the two quadratic invariants that are needed to construct the energy-momentum tensor, namely the Rayleigh dissipation function and Lagrangian for perturbations. Finally, we develop the notion that the viscoelastic behavior of the medium can be thought of as a non-minimally coupled massive gravity theory. This also provides a tool-kit for constructing consistent generalizations of coupled dark energy theories. Contents

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Modified gravity and cosmology

Cited by 3,864 publications

References 1,166 publications

Inflation and primordial non-Gaussianities of “generalized Galileons”

Inflation and primordial non-Gaussianities of “generalized Galileons”

Model‐independent constraints on r^‐3 extra‐interactions from orbital motions

Material models of dark energy

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Modified gravity and cosmology

Cited by 3,864 publications

References 1,166 publications

Inflation and primordial non-Gaussianities of “generalized Galileons”

Inflation and primordial non-Gaussianities of “generalized Galileons”

Model‐independent constraints on r‐3 extra‐interactions from orbital motions

Material models of dark energy

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Product

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Model‐independent constraints on r^‐3 extra‐interactions from orbital motions