Evolution of the cosmological equation of state with SNeIa, BAO and high redshift GRBs
Sergey Postnikov
Indiana University
We study the dark energy equation of state as a function of redshift in a nonparametric way, without imposing any a priori w(z) (ratio of pressure over energy density) functional form. As a check of the method, we test our scheme through the use of synthetic data sets produced from different input cosmological models which have the same relative errors and redshift distribution as the real data. Using the luminositytime LXTa correlation for GRB Xray afterglows (the Dainotti et al. correlation), we are able to utilize GRB sample from the Swift satellite as probes of the expansion history of the Universe out to z≅10. Within the assumption of a flat FLRW universe and combining SNeIa data with BAO constraints, the resulting maximum likelihood solutions are close to a constant w=1. If one imposes the restriction of a constant w, we obtain w=0.99±0.06 (consistent with a cosmological constant) with the present day Hubble constant as H0=70.0±0.6 km s1 Mpc1 and density parameter as ΩΛ0=0.723±0.025, while nonparametric w(z) solutions give us a probability map which is centred at H0=70.04±1 km s1 Mpc1 and ΩΛ0=0.724±0.03. Our chosen GRB data sample with full correlation matrix allows us to estimate the amount, as well as quality (errors) of data, needed to constrain w(z) in the redshift range extending an order of magnitude in beyond the farthest SNeIa measured.
Date:  Friday, 31 January 2014 
Time:  14:00 
Where:  McGill University 
 Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103) 
Contact:  Robert Rutledge 
