Vitagliano 2009 高红移宇宙学

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Title:		High-redshift cosmography
Authors:		Vitagliano, Vincenzo; Xia, Jun-Qing; Liberati, Stefano; Viel, Matteo
Affiliation:		AA(SISSA, Via Beirut 2-4, 34151 Trieste, Italy ; INFN sez. Trieste, Via Valerio 2, 34127 Trieste, Italy ), AB(SISSA, Via Beirut 2-4, 34151 Trieste, Italy ), AC(SISSA, Via Beirut 2-4, 34151 Trieste, Italy ; INFN sez. Trieste, Via Valerio 2, 34127 Trieste, Italy ), AD(INFN sez. Trieste, Via Valerio 2, 34127 Trieste, Italy ; INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste, Italy)
Publication:		Journal of Cosmology and Astroparticle Physics, Issue 03, pp. 005 (2010). (JCAP Homepage)
Publication Date:		03/2010
Origin:		IOP
DOI:		10.1088/1475-7516/2010/03/005
Bibliographic Code:		2010JCAP...03..005V

Abstract

We constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires a very minimal set of assumptions (namely to specify a metric) and does not rely on the dynamical equations for gravity. On the data side, we consider the most recent compilations of Supernovae and Gamma Ray Bursts catalogues. This allows to further extend the cosmographic fit up to z = 6.6, i.e. up to redshift for which one could start to resolve the low z degeneracy among competing cosmological models. In order to reliably control the cosmographic approach at high redshifts, we adopt the expansion in the improved parameter y = z/(1+z). This series has the great advantage to hold also for z > 1 and hence it is the appropriate tool for handling data including non-nearby distance indicators. We find that Gamma Ray Bursts, probing higher redshifts than Supernovae, have constraining power and do require (and statistically allow) a cosmographic expansion at higher order than Supernovae alone. Exploiting the set of data from Union and GRBs catalogues, we show (for the first time in a purely cosmographic approach parametrized by deceleration q₀, jerk j₀, snap s₀) a definitively negative deceleration parameter q₀ up to the 3σ confidence level. We present also forecasts for realistic data sets that are likely to be obtained in the next few years.

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