2004/07/31 by Bruce A. Bassett, Pier-Stefano Corasaniti, Pier Stefano Corasaniti +2 · 12 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/427023
published as Astrophys.J. 617 (2004) L1-L4 · 7 pages, 4 colour figures, EmulateApJ; v2: includes Bayesian evidence analysis and table that were only present in published version, because of increased interest in Bayesian model comparison (no new material beyond the one in the published ApJL of 2004)
openalex publication_date 2004/11/03 · arxiv created 2007/03/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Standard two-parameter compressions of the infinite dimensional dark energy model space show crippling limitations even with current Type Ia supernova (SN Ia) data unless strong priors are imposed. First, they cannot cope with rapid evolution—our best fit to the latest SN Ia data shows late and very rapid evolution to w 0 = -2.85. However, all of the standard parameterizations (incorrectly) claim that this best fit is ruled out at more than 2 σ primarily because they track it well only at very low redshift, z ≤ 0.2. Furthermore, they incorrectly rule out the observationally compatible region w ≪ -1 for z > 1. Second, the parameterizations give wildly different estimates for the redshift of acceleration, which vary from z acc = 0.14 to z acc = 0.59. Although these failings are largely cured by including higher order terms (≥3 parameters), this results in new degeneracies and opens up large regions of previously ruled out parameter space. All of this casts serious doubt on the usefulness of the standard two-parameter compressions in the coming era of high-precision dark energy cosmology and emphasizes the need for decorrelated compressions with at least three parameters.