High-resolution temporal constraints on the dynamics of dark energy

We use the recent Type Ia supernova, cosmic microwave background and large-scale structure data to shed light on the temporal evolution of the dark energy equation of state $w(z)$ out to redshift one. We constrain the most flexible parametrization of dark energy to date, and include the dark energy perturbations consistently throughout. Interpreting our results via the principal component analysis, we find no significant evidence for dynamical dark energy: the cosmological constant model is consistent with data everywhere between redshift zero and one at 95% C.L.

Figure 1

Reconstruction of $w(z)$ using the data sets I (top panel) and II (bottom panel); see text for details. The inner (red) and outer (black) error bars correspond to 68% and 95% error bars, respectively. The $\Lambda \mathrm{CDM}$ model is shown with the dashed (blue) line. In the bottom panel, we also plot the reconstruction result with an alternative placement of fitting nodes (points and curve; see text for details).

Figure 2

Constraints on uncorrelated band powers of the equation of state $w(z)$, using the data set II. (a), (b) median values and the 68% and 95% constraints on the localized principal components ${\mathbf{q}}_1$, and their weights in redshift ${\mathbf{W}}_1$, respectively.(c), (d) same for the principal components ${\mathbf{q}}_2$ and their weights ${\mathbf{W}}_2$ (see the text for definitions). (e) likelihood distributions for the parameters ${\mathbf{q}}_1$;(f) reduction in ${\chi }^2$ relative to $\Lambda \mathrm{CDM}$ as the number of fitting nodes (for parameters ${\mathbf{q}}_1$) is increased.