Previous studies have shown that the cosmic expansion is accelerating despite the gravitational attraction between matter, caused by a mysterious source of energy denoted as dark energy. A cosmographic test of whether it exists in the form of a cosmological constant or more general dark energy was performed with Markov chain Monte Carlo algorithms using the SCP Union2.1 supernova compilation. By fitting polynomials to Hubble series expansions, the Hubble Constant (H0), the deceleration parameter (q0), and the jerk parameter (j0) can be estimated … This study focuses on the effects of MCMC algorithms and model-building uncertainty the dependence of results based on fitting functions used. Eight tests of different orders and distance scales were performed. Through a new program devised in Java, resulting uncertainties of all parameters are significantly smaller than those from traditional statistical techniques. Combined with cosmographic method, MCMC yields much more Gaussian distributions of cosmological parameters.

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• Astronomy
• Physics