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Cosmic Curvature (standard ruler)
Some of the most important parameters of the metric are those that directly affect the curvature of three-dimensional comoving spatial sections.
![metric parameters image](/foswiki/pub/Cosmo/CosmoCurvature/../CosmoProjectsBrief/metric_par.jpg)
This mainly includes
![\Omega_m](/foswiki/pub/Cosmo/CosmoCurvature/_MathModePlugin_5c2c07ae5be3f5ac043ddd56c026a056.png)
and
![\Omega_\Lambda](/foswiki/pub/Cosmo/CosmoCurvature/_MathModePlugin_ac22fd1fc9efa90d3d90f4addc81a194.png)
. The first (and possibly the only, so far) simultaneous constraint on both
![\Omega_m](/foswiki/pub/Cosmo/CosmoCurvature/_MathModePlugin_5c2c07ae5be3f5ac043ddd56c026a056.png)
and
![\Omega_\Lambda](/foswiki/pub/Cosmo/CosmoCurvature/_MathModePlugin_ac22fd1fc9efa90d3d90f4addc81a194.png)
from within a single survey, using a standard ruler method, is
AstroPh:0106135 - Roukema, Mamon, Bajtlik (2002). This topic is generally referred to today as BAO - the use of baryonic acoustic oscillations - although in fact can be more general, i.e. make less assumptions. The best-cited example of BAO usage is
AstroPh:0501171 SDSS z < 0.47 Eisenstein et al., who estimated Omega_total = 1.010\pm0.009. Updating Roukema, Mamon & Bajtlik (2002) on newer QSO redshift surveys should result in preciser, and hopefully more accurate, estimates of these metric parameters.