title: Model-independent dark energy differentiation with the integrated Sachs-Wolfe effect.
abstract: We study the integrated Sachs-Wolfe effect using a model-independent parametrization of the dark energy equation of state, w(z). Cosmic variance severely restricts the class of models distinguishable from one based on cold dark matter and a cosmological constant unless w(z) currently satisfies w(o)(Q)>-0.8, or exhibits a rapid, late-time, transition at redshifts z<3. Because of the degeneracy with other cosmological parameters, models with a slowly varying w(z) cannot be differentiated from each other or from a cosmological constant. This may place a fundamental limit on our understanding of the origin of the currently observed acceleration.
authors.affiliation: Centre for Theoretical Physics, University of Sussex, Falmer, Brighton, BN1 9QJ, United Kingdom.
authors.forename: P S
authors.initials: PS
authors.lastname: Corasaniti
authors.forename: B A
authors.initials: BA
authors.lastname: Bassett
authors.forename: C
authors.initials: C
authors.lastname: Ungarelli
authors.forename: E J
authors.initials: EJ
authors.lastname: Copeland