Orlando Luongo

Cosmographyand constraints onthe equation of state ofthe Universe invarious parametrizations

We use cosmography to present constraints on the kinematics of the Universe, without postulating any underlying theoretical model. To this end, we use a Monte Carlo Markov Chain analysis to perform comparisons to the supernova Ia Union 2 compilation, combined with the Hubble Space Telescope measurements of the Hubble constant, and the Hubble parameter datasets. We introduce a sixth order cosmographic parameter and show that it does not enlarge considerably the posterior distribution when comparing to the fifth order results. We also propose a way to construct viable parameter variables to be used as alternatives of the redshift

Cosmographic bounds on the cosmological deceleration-acceleration transition redshift in f ( R ) gravity

z

Updated constraints on f(R) gravity from cosmography

. These can overcome both the problems of divergence and lack of accuracy associated with the use of

Cosmographic Constraints and Cosmic Fluids

z

Cosmographic reconstruction of

. Moreover, we show that it is possible to improve the numerical fits by re-parameterizing the cosmological distances. In addition, we constrain the equation of state of the Universe as a whole by the use of cosmography. Thus, we derive expressions which can be directly used to fit the equation of state and the pressure derivatives up to fourth order. To this end, it is necessary to depart from a pure cosmographic analysis and to assume the Friedmann equations as valid. All our results are consistent with the

f(\mathcal{T})

\Lambda

cosmology

CDM model, although alternative fluid models, with nearly constant pressure and no cosmological constant, match the results accurately as well.

CONNECTING EARLY AND LATE UNIVERSE BY f(R) GRAVITY

We examine the observational viability of a class of

Model-independent limits and constraints on extended theories of gravity from cosmic reconstruction techniques

f(\mathcal{R})

A UNIFIED DARK ENERGY MODEL FROM A VANISHING SPEED OF SOUND WITH EMERGENT COSMOLOGICAL CONSTANT

gravity cosmological models. Particular attention is devoted to constraints from the recent observational determination of the redshift of the cosmological deceleration-acceleration transition. Making use of the fact that the Ricci scalar is a function of redshift