Topic
Cosmography
About: Cosmography is a research topic. Over the lifetime, 230 publications have been published within this topic receiving 3126 citations.
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TL;DR: In this article, the authors consider the case of teleparallel gravity also referred to as $f(T)$ gravity and derive the present day values of the derivatives as a function of cosmographic parameters.
Abstract: Based only on the assumption that the Universe is homogenous and isotropic on large scales, cosmography is an ideal tool to investigate the cosmic expansion history in an almost model-independent way. Fitting the data on the luminosity distance and baryon acoustic oscillations allows to determine the confidence ranges for the cosmographic parameters hence giving some quantitative constraints that at whatever theory has to fulfill. As an application, we consider here the case of teleparallel gravity also referred to as $f(T)$ gravity. To this end, we first work out analytical expressions to express the present day values of $f(T)$ derivatives as a function of the cosmographic parameters, which hold under quite general and physically motivated conditions. We then use the constraints coming from cosmography to find out the confidence ranges for $f(T)$ derivatives up to the fifth order and show how these can be used to check the viability of given teleparallel gravity models without the need to explicitly solve the second order dynamic equations.
290 citations
TL;DR: In this paper, the success and the shortcomings of the ΛCDM model, based on cosmography, are discussed and a review of the model's performance is presented. But the model is not considered as a sort of a model-independent approach to tackle the dark energy/modified gravity problem.
Abstract: Cosmography can be considered as a sort of a model-independent approach to tackle the dark energy/modified gravity problem. In this review, the success and the shortcomings of the ΛCDM model, based...
262 citations
TL;DR: In this paper, the authors explore the extent to which cosmography is sufficient for analyzing the Hubble law and so describing many of the features of the universe around us, and show that it is not necessary to satisfy the Friedmann equations.
Abstract: How much of modern cosmology is really cosmography? How much of modern cosmology is independent of the Einstein equations? (Independent of the Friedmann equations?) These questions are becoming increasingly germane—as the models cosmologists use for the stress-energy content of the universe become increasingly baroque, it behaves us to step back a little and carefully disentangle cosmological kinematics from cosmological dynamics. The use of basic symmetry principles (such as the cosmological principle) permits us to do a considerable amount, without ever having to address the vexatious issues of just how much “dark energy”, “dark matter”, “quintessence”, and/or “phantom matter” is needed in order to satisfy the Einstein equations. This is the sub-sector of cosmology that Weinberg refers to as “cosmography”, and in this article I will explore the extent to which cosmography is sufficient for analyzing the Hubble law and so describing many of the features of the universe around us.
260 citations
TL;DR: In this article, a Monte Carlo Markov chain analysis is used to compare the supernova Ia Union 2 compilation, combined with the Hubble Space Telescope measurements of the Hubble constant, and the Hubble parameter data sets.
Abstract: 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 data sets. 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 $z$. These can overcome both the problems of divergence and lack of accuracy associated with the use of $z$. Moreover, we show that it is possible to improve the numerical fits by reparametrizing 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 $\ensuremath{\Lambda}\mathrm{CDM}$ model, although alternative fluid models, with nearly constant pressure and no cosmological constant, match the results accurately as well.
227 citations
Book•
01 Jan 1968
TL;DR: In this article, the Universal Figures of Islamic Science, the basis of the teaching system and the educational institutions of Islam, and the perspectives of Islam within the Islamic Civilization are discussed.
Abstract: Introduction A. The Principles of Islam B. The Perspectives within Islamic Civilization 1. The Universal Figures of Islamic Science 2. The Basis of the Teaching System and the Educational Institutions 3. Cosmology, Cosmography, Geography, and Natural History 4. Physics 5. Mathematics 6. Astronomy 7. Medicine 8. The Sciences of Man 9. The Alchemical Tradition 10. Islamic Alchemy and its Influence in the Western World 11. Philosophy 12. The Controversies of Philosophy and Theology 13. The Gnostic Tradition Selected Bibliography Index.
207 citations