Modifications of gravity: what can we measure in principle?

by Dr Ignacy Sawicki (Heidelberg)

Wednesday 6 Mar 2013, 11:30 → 12:30 Europe/Zurich

4/2-011 - TH common room (CERN)

The difference between various models of dark energy or modifications of gravity becomes apparent at the level of growth of large-scale structure in the universe. In addition to measuring the background expansion, we are now beginning to probe this aspect. The problem that is not particularly understood currently is the impact of the assumption of a particular model of dark energy on the interpretation of observations. I will show that we in principle cannot disentangle the contribution of dark matter from that of dark energy to neither the evolution of the cosmological background nor that of large-scale structure unless a model is assumed in the first place. This degeneracy limits severely the measurements that we can obtain. I will discuss the total set of model-independent observables that we can obtain from the sky and will discuss how we could in principle rule out various classes of generalised Galileons as models of cosmic acceleration in their entirety.