22-26 August 2011, Porto, Portugal
Probing modified gravity with Euclid-like spectroscopic surveys We explore the ability of future redshift surveys of galaxies to estimate the growth rate of structure from measurements of the amplitude and redshift-space anisotropy of galaxy clustering, probing in this way the possibility that gravity is modified on large scales. We do this in the context of a survey which measures in addition the expansion history of the Universe, using the power spectrum (and its baryonic features) as a standard ruler, and explore the relative degeneracies of measurements of expansion and growth. We forecast an error on fsigma_8 between 1.6% and 4.8%, depending on model assumptions. We investigate the important aspect of how sensitive the optimal survey configuration is to the way we parameterize growth and to the cosmological model we assume, stressing how specific parameterizations could actually drive the design towards artificially restricted regions of a survey's parameter space. If however we use the growth index parameter, our reference survey, the current baseline of the planned Euclid slitless spectroscopic survey, should be able to distinguish modified gravity models having |gamma-0.55| greater than 0.12. |
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