Testing Lambda and the Limits of Cosmography with the Union2.1 Supernova Compilation

Understand

We present a cosmographic study designed to test the simplest type of accelerating cosmology: a flat universe with matter and a cosmological constant ($\Lambda$).

• Hubble series expansions are fit to the SCP Union2.1 supernova data set to estimate the Hubble Constant ($H_{0}$), the deceleration parameter ($q_{0}$), and the jerk parameter ($j_{0}$).
• Flat $\Lambda$CDM models always require $j_{0} = 1$, providing a single-parameter test of the entire paradigm.
• Because of convergence issues for $z \gtrsim 1$, we focus on expansions using the newer redshift variable $y$, and to estimate the effects of "model-building uncertainties" -- the dependence of the output results upon the fitting function and parameters used -- we perform fits using five different distance indicator functions, and four different polynomial orders.