Figure of Merit for Dark Energy Constraints from Current Observational Data
| dc.creator | Wang, Yun | |
| dc.date | 2008-03-31 | |
| dc.date.accessioned | 2026-07-07T11:49:26Z | |
| dc.date.available | 2026-07-07T11:49:26Z | |
| dc.description | Choosing the appropriate figure of merit (FoM) for dark energy (DE) constraints is key in comparing different DE experiments. Here we show that for a set of DE parameters {f_i}, it is most intuitive to define FoM = 1/\sqrt{Cov(f1,f2,f3,...)}, where Cov(f1,f2,f3,...) is the covariance matrix of {f_i}. The {f_i} should be minimally correlated. We demonstrate two useful choices of {f_i} using 182 SNe Ia (compiled by Riess et al. 2007), [R(z_*), l_a(z_*), Ω_b h^2] from the five year Wilkinson Microwave Anisotropy Probe (WMAP) observations, and SDSS measurement of the baryon acoustic oscillation (BAO) scale, assuming the HST prior of H_0=72+/-8 km/s Mpc^{-1} and without assuming spatial flatness. We find that the correlation of (w_0,w_{0.5}) [w_0=w_X(z=0), w_{0.5}=w_X(z=0.5), w_X(a) = 3w_{0.5}-2w_0+3(w_0-w_{0.5})a] is significantly smaller than that of (w_0,w_a) [w_X(a)=w_0+(1-a)w_a]. In order to obtain model-independent constraints on DE, we parametrize the DE density function X(z)=ρ_X(z)/ρ_X(0) as a free function with X_{0.5}, X_{1.0}, and X_{1.5} [values of X(z) at z=0.5, 1.0, and 1.5] as free parameters estimated from data. If one assumes a linear DE equation of state, current data are consistent with a cosmological constant at 68% C.L. If one assumes X(z) to be a free function parametrized by (X_{0.5}, X_{1.0}, X_{1.5}), current data deviate from a cosmological constant at z=1 at 68% C.L., but are consistent with a cosmological constant at 95% C.L.. Future DE experiments will allow us to dramatically increase the FoM of constraints on (w_0,w_{0.5}) and of (X_{0.5}, X_{1.0}, X_{1.5}). This will significantly shrink the DE parameter space to enable the discovery of DE evolution, or the conclusive evidence for a cosmological constant. | |
| dc.description | 7 pages, 3 color figures. Submitted | |
| dc.identifier | https://arxiv.org/abs/0803.4295 | |
| dc.identifier | http://arxiv.org/abs/0803.4295 | |
| dc.identifier | Phys.Rev.D77:123525,2008 | |
| dc.identifier | doi:10.1103/PhysRevD.77.123525 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/203236 | |
| dc.subject | Astrophysics | |
| dc.title | Figure of Merit for Dark Energy Constraints from Current Observational Data | |
| dc.type | text |