title: A gravitational puzzle.
abstract: The challenge to understand the physical origin of the cosmic acceleration is framed as a problem of gravitation. Specifically, does the relationship between stress-energy and space-time curvature differ on large scales from the predictions of general relativity. In this article, we describe efforts to model and test a generalized relationship between the matter and the metric using cosmological observations. Late-time tracers of large-scale structure, including the cosmic microwave background, weak gravitational lensing, and clustering are shown to provide good tests of the proposed solution. Current data are very close to proving a critical test, leaving only a small window in parameter space in the case that the generalized relationship is scale free above galactic scales.
authors.affiliation: Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA. robert.r.caldwell@dartmouth.edu
authors.forename: Robert R
authors.initials: RR
authors.lastname: Caldwell