Beyond Two Dark Energy Parameters

Our ignorance of dark energy is generally described by a two-parameter equation of state. In these approaches, a particular ad hoc functional form is assumed, and only two independent parameters are incorporated. We propose a model-independent, multiparameter approach to fitting dark energy and show that next-generation surveys will constrain the equation of state in three or more independent redshift bins to better than 10%. Future knowledge of dark energy will surpass two numbers (e.g., $[w_0,w_1]$ or $[w_0,w_a]$), and we propose a more flexible approach to the analysis of present and future data.

Figure 1

Uncorrelated binned estimates of the EOS from a typical mock sample generated for cases C (top panel) and E (bottom panel). The error bars show $1\sigma$ and $2\sigma$ uncertainties with solid and dashed lines, respectively. At the bottom, in separate colors, we show the window function for each of the independent, decorrelated bins. The overlap in window functions represents the relative contribution from adjacent redshifts bins to each uncorrelated $w(z_i)$ estimate.