Yun Wang's Group's Dark Energy Measurements

Results from Wang, Chuang, & Mukherjee (2012), arXiv:1109.3172 (Phys. Rev. D 85, 023517 (2012)): Dark energy density as a function of cosmic time, in units of yoctograms [10**(-24) grams] per cubic meter, measured from the data of 472 SNe compiled by Conley et al. (2011), with the galaxy clustering measurements from the Sloan Digital Sky Survey data by Chuang & Wang (2011), the cosmic microwave background anisotropy data from WMAP seven year observations (Komatsu et al. 2011), model-independent distances measured from 69 gamma-ray bursts (Wang 2008), and Hubble constant measuement by Riess et al. (2011). The 68% (shaded) and 95% confidence level regions are shown. The cosmological redshift z is an indicator of cosmic time; the universe is approximately 14 Giga yrs old today (z=0), and approximately 6 Giga yrs old at z=1. A cosmological constant is indicated by the thick dashed black line. The green contours indicate the matter density. Thanks to Max Tegmark for suggesting this alternative presentation of the results.

Fig. 15 from Wang, Chuang, & Mukherjee (2012), arXiv:1109.3172. This is the same as the figure above, but in units of rho_X(0) (the dark energy density today). The errors are not shown for rho_m(z).

Fig. 16 from Wang, Chuang, & Mukherjee (2012), arXiv:1109.3172. The measured cosmic expansion history H(z) corresponding to the above measurement of dark energy density function. The error bars represent the 68% confidence level. The lower panel shows [da/dt] divided by the Hubble constant, where a is the cosmic scale factor; this clearly shows that the expansion of the universe began to accelerate recently (at redshift z~0.5). Note that H(z)=[da/dt]/a.