1998/05/13 by James C. Robinson, James Robinson, Eric Gawiser +4
Physics and Astronomy · #Astrophysics (astro-ph) #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #FOS: Physical sciences #Particle physics theoretical and experimental studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9805181
Six pages including 3 postscript figures, submitted to Astrophysical Journal Letters
arxiv created 1998/05/13 · openalex publication_date 1998/05/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider constraints on the amplitude of mass fluctuations in the universe, sigma8, derived from two simple observations: the present number density of clusters and the amplitude of their correlation function. Allowing for the possibility that the primordial fluctuations are non-gaussian introduces a degeneracy in the value of sigma8 preferred by each of these constraints. However, when the constraints are taken together this degeneracy is broken, yielding a precise determination of sigma8 and the degree of non-gaussianity for a given background cosmology. For a flat, Omegam=1 universe with a power spectrum parameterized by a CDM shape parameter Gamma=0.2, we find that the perturbations are consistent with a gaussian distribution with sigma8=0.49(+0.08-0.07) (95% limits). For some popular choices of background model, including the favored low matter density models, the hypothesis that the primordial fluctuations are gaussian is ruled out with a high degree of confidence.