Model-independent reconstruction of f(T) teleparallel cosmology |
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Authors: | Salvatore Capozziello,Rocco D’Agostino,Orlando Luongo |
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Affiliation: | 1.Dipartimento di Fisica,Università di Napoli “Federico II”,Naples,Italy;2.Istituto Nazionale di Fisica Nucleare (INFN), Sez. di Napoli,Naples,Italy;3.Gran Sasso Science Institute,L’ Aquila,Italy;4.Dipartimento di Fisica,Università degli Studi di Roma “Tor Vergata”,Rome,Italy;5.Istituto Nazionale di Fisica Nucleare (INFN), Sez. di Roma “Tor Vergata”,Rome,Italy;6.School of Science and Technology,University of Camerino,Camerino,Italy;7.Department of Mathematics and Applied Mathematics,University of Cape Town,Cape Town,South Africa;8.Astrophysics, Cosmology and Gravity Centre (ACGC),University of Cape Town,Cape Town,South Africa |
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Abstract: | We propose a model-independent formalism to numerically solve the modified Friedmann equations in the framework of f(T) teleparallel cosmology. Our strategy is to expand the Hubble parameter around the redshift (z=0) up to a given order and to adopt cosmographic bounds as initial settings to determine the corresponding (f(z)equiv f(T(H(z)))) function. In this perspective, we distinguish two cases: the first expansion is up to the jerk parameter, the second expansion is up to the snap parameter. We show that inside the observed redshift domain (zle 1), only the net strength of f(z) is modified passing from jerk to snap, whereas its functional behavior and shape turn out to be identical. As first step, we set the cosmographic parameters by means of the most recent observations. Afterwards, we calibrate our numerical solutions with the concordance (Lambda )CDM model. In both cases, there is a good agreement with the cosmological standard model around (zle 1), with severe discrepancies outer of this limit. We demonstrate that the effective dark energy term evolves following the test-function: (f(z)={mathcal {A}}+{mathcal {B}}{z}^2e^{{mathcal {C}}{z}}). Bounds over the set (left{ {mathcal {A}}, {mathcal {B}}, {mathcal {C}}right} ) are also fixed by statistical considerations, comparing discrepancies between f(z) with data. The approach opens the possibility to get a wide class of test-functions able to frame the dynamics of f(T) without postulating any model a priori. We thus re-obtain the f(T) function through a back-scattering procedure once f(z) is known. We figure out the properties of our f(T) function at the level of background cosmology, to check the goodness of our numerical results. Finally, a comparison with previous cosmographic approaches is carried out giving results compatible with theoretical expectations. |
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