Alejandro Aviles

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

Updated constraints on f(R) gravity from cosmography

z

Extending the generalized Chaplygin gas model by using geometrothermodynamics

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

Cosmographic reconstruction of

z

f(\mathcal{T})

. 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

cosmology

\Lambda

Cyclic brightening in the short-period WZ Sge-type cataclysmic variable SDSS J080434.20+510349.2

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

The accretion disk in the post period-minimum cataclysmic variable SDSS J080434.20 + 510349.2

We address the issue of constraining the class of

Holographic dark matter and dark energy with second order invariants

f(\mathcal{R})

Dark matter from dark energy-baryonic matter couplings

gravity able to reproduce the observed cosmological acceleration, by using the so-called cosmography of the Universe. We consider a model independent procedure to build up a