Probing Dark Energy and Gravity with Distance and Growth Measurements

Presented by Dr. Hu Zhan, University of California, Davis

The accelerated cosmic expansion suggests that either the universe is dominated by dark energy, a smooth, inert component that has strong negative pressure, or the standard cosmological framework based on General Relativity is inadequate. Since it is not yet possible to observe dark energy or modified gravity directly, one has to rely on indirect measurements, such as the cosmic distance scale and the growth of large-scale density fluctuations as functions of redshift. I will discuss two probes that provide such measurements: weak lensing and baryon acoustic oscillations and present estimates of distance and growth constraints for the Large Synoptic Survey Telescope project. The reconstructed distance and growth factor can then be projected to constrain the parameters of a specific dark energy or modified gravity model. Further examples will be given to disentangle the roles of the distance and growth rate in constraining the dark energy equation-of-state parameters and to demonstrate the complementarity between the two probes. Finally, I will mention how and how well the mean curvature of the universe can be determined from future surveys.