Reconstruction procedure in nonlocal cosmological models

Elizalde, E.; Pozdeeva, Ekaterina; Vernov, S. Yu.

doi:10.1088/0264-9381/30/3/035002

Cited by 48 publications

(54 citation statements)

References 106 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After studying some very well known f (R) cosmological models, as a general remark we have to note that the effect of collisional matter to f (R) models is strongly model dependent. Particularly, the models appearing in equations, (36) and (39) result to q(z) and w ef f curves which are more similar to the ΛCDM curves, in comparison to the pressure-less matter f (R) theories. In addition, the transition redshift that the models (36) and (39) predict are much more closer to the ΛCDM curves, again in reference to pressure-less matter f (R) theories.…”

Section: Discussionmentioning

confidence: 90%

Late-time cosmological evolution in f ( R ) theories with ordinary and collisional matter

Oikonomou

Karagiannakis

2015

Class. Quantum Grav.

View full text Add to dashboard Cite

We study the late time cosmological evolution of f (R) theories of modified gravity, with the matter content of the universe being that of collisional self interacting matter. We assume that the universe is described by a flat Friedmann-Lemaitre-RobertsonWalker metric and that it is matter and dark energy dominated. The results of our numerical analysis for a collisional matter f (R) theory are compared with those resulting from pressure-less matter f (R) theory and from the ΛCDM model. As we shall demonstrate, the resulting picture can vary from model to model, indicating that the effect of collisional matter in f (R) theories is strongly model dependent. Particularly, in a few cases, may give better fit to the ΛCDM model. In all studied cases, the effective equation of state parameter does not cross the phantom divide, both in the collisional matter and pressure-less matter f (R) theories. Finally, we thoroughly study the effects of collisional matter on one of the f (R) models that is known to provide a unified description of early time inflation and late time acceleration. The overall picture of the evolution of the universe is not drastically affected, apart from the matter era which is further enhanced with an additional matter energy density term, which is of leading order. However, a fully consistent description of the universe's evolution requires the introduction of a dark energy compensate in the total energy density, a concept very well known from the literature. * voiko@physics.auth.gr † nikar@auth.gr

show abstract

Section: Discussionmentioning

confidence: 90%

Late-time cosmological evolution in f ( R ) theories with ordinary and collisional matter

Oikonomou

Karagiannakis

2015

Class. Quantum Grav.

View full text Add to dashboard Cite

show abstract

“…The integral dependence of the corrections could generate the observed acceleration at the present cosmological epoch dynamically and without special fine-tunings. However, detailed investigations have shown that, although the function f can be chosen in such a way that the background expansion is consistent with the data [21][22][23] and the model has a viable Newtonian limit [24,25], the impact of the nonlocal corrections on the evolution of perturbations is strong and utterly rules the model out when this is confronted with large-scale structure data [26]. On top of that, nonlocal modifications of gravity result generically in instabilities at the level of perturbations, at least if they involve tensorial terms such as (W µνρσ / 2 )W µνρσ [27] with W µνρσ the Weyl tensor appearing in models inspired by the conformal anomaly [28,29].…”

Section: Introductionmentioning

confidence: 99%

Dynamical analysis ofR1□2Rcosmology: Impact of initial conditions and constraints from supernovae

et al. 2016

View full text Add to dashboard Cite

We discuss the cosmological implications of the R −2 R nonlocal modification to standard gravity. We relax the assumption of special initial conditions in the local formulation of the theory, perform a full phase-space analysis of the system, and show that the late-time cosmology of the model exhibits two distinct evolution paths, on which a large range of values for the present equation of state can be reached. We then compare the general solutions to supernovae data and place constraints on the parameters of the model. In particular, we find that the mass parameter of the theory should be smaller than 1.2 in Hubble units.

show abstract

“…[77][78][79][80][81][82][83][84][85][86][87]. In this approach there is no basic principle that fixes the function f (✷ −1 R), which is therefore chosen on purely phenomenological grounds, and can be reconstructed so to fit any given expansion history [88,89]. In our case, in contrast, the non-local Friedmann equation follows from eq.…”

Section: Introductionmentioning

confidence: 99%

Nonlocal theory of massive gravity

2013

View full text Add to dashboard Cite

We construct a fully covariant theory of massive gravity which does not require the introduction of an external reference metric, and overcomes the usual problems of massive gravity theories (fatal ghosts instabilities, acausality and/or vDVZ discontinuity). The equations of motion of the theory are non-local, but respect causality. The starting point is the quadratic action proposed in the context of the degravitation idea. We show that it is possible to extended it to a fully non-linear covariant theory. This theory describes the five degrees of freedom of a massive graviton plus a scalar ghost. However, contrary to generic non-linear extensions of Fierz-Pauli massive gravity, the ghost has the same mass m as the massive graviton, independently of the background, and smoothly goes into a non-radiative degree of freedom for m → 0. As a consequence, for m ∼ H 0 the vacuum instability induced by the ghost is irrelevant even over cosmological time-scales. We finally show that an extension of the model degravitates a vacuum energy density of order M 4 Pl down to a value of order M 2 Pl m 2 , which for m = O(H 0 ) is of order of the observed value of the vacuum energy density.

show abstract

Reconstruction procedure in nonlocal cosmological models

Cited by 48 publications

References 106 publications

Late-time cosmological evolution in f ( R ) theories with ordinary and collisional matter

Late-time cosmological evolution in f ( R ) theories with ordinary and collisional matter

Dynamical analysis ofR1□2Rcosmology: Impact of initial conditions and constraints from supernovae

Nonlocal theory of massive gravity

Contact Info

Product

Resources

About