Mariafelicia De Laurentis

No further gravitational wave modes in

Abstract We explore the possibility of further gravitational wave modes in F ( T ) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F ( T ) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F ( T ) . This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F ( T ) gravity.

F(T)

The problem of reproducing dark energy effects is reviewed here with particular interest devoted to cosmography. We summarize some of the most relevant cosmological models, based on the assumption that the corresponding barotropic equations of state evolve as the universe expands, giving rise to the accelerated expansion. We describe in detail the CDM ( -Cold Dark Matter) and!CDM models, considering also some specific examples, e.g., Chevallier-Polarsky-Linder, the Chaplygin gas and the Dvali-Gabadadze-Porrati cosmological model. Finally, we consider the cosmological consequences off(R) andf(T ) gravities and their impact on the framework of cosmography. Keeping these considerations in mind, we point out the model-independent procedure related to cosmography, showing how to match the series of cosmological observables to the free parameters of each model. We critically discuss the role played by cosmography, as a selection criterion to check whether a particular model passes or does not present cosmological constraints. In so doing, we find out cosmological bounds by fitting the luminosity distance expansion of the redshift,z, adopting the recent Union 2.1 dataset of supernovae, combined with the baryonic acoustic oscillation and the cosmic microwave background measurements. We perform cosmographic analyses, imposing different priors on the Hubble rate present value. In addition, we compare our results with recent PLANCK limits, showing that the CDM and !CDM models seem to be the favorite with respect to other dark energy models. However, we show that cosmographic constraints on f(R) and f(T ) cannot discriminate between

gravity

Over the past few decades, general relativity and the concordance ΛCDM model have been successfully tested using several different astrophysical and cosmological probes based on large datasets (precision cosmology). Despite their successes, some shortcomings emerge due to the fact that general relativity should be revised at infrared and ultraviolet limits and to the fact that the fundamental nature of dark matter and dark energy is still a puzzle to be solved. In this perspective, ƒ(R) gravity has been extensively investigated, being the most straightforward way to modify general relativity and to overcame some of the above shortcomings. In this paper, we review various aspects of ƒ(R) gravity at extragalactic and cosmological levels. In particular, we consider a cluster of galaxies, cosmological perturbations and N-body simulations, focusing on those models that satisfy both cosmological and local gravity constraints. The perspective is that some classes of ƒ(R) models can be consistently constrained by the large-scale structure.

Cosmographic Constraints and Cosmic Fluids

Inflation and dark energy are two of the most relevant aspects of modern cosmology. These different epochs provide the universe is passing through accelerated phases soon after the Big-Bang and at present stage of its evolution. In this review paper, we discuss that both eras can be, in principle, described by a geometric picture, under the standard of

Constraining f(R) Gravity by the Large-Scale Structure

f(R)

CONNECTING EARLY AND LATE UNIVERSE BY f(R) GRAVITY

gravity. We give the fundamental physics motivations and outline the main ingredients of

Dark Matter in galaxies: leads to its Nature

f(R)

Curvature dark energy reconstruction through different cosmographic distance definitions

inflation, quintessence and cosmography. This wants to be a quick summary of

FURTHER GRAVITATIONAL WAVE MODES FROM HIGHER ORDER GRAVITY

f(R)

The SKA contribution to GRB cosmology

paradigm without claiming of completeness.