Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-09-08
Phys.Rev.D72:103515,2005
Astronomy and Astrophysics
Astrophysics
12 pages, 8 figures. Some references added. PRD in press
Scientific paper
10.1103/PhysRevD.72.103515
Various recent studies proved that cosmological models with a significant contribution from cold dark matter isocurvature perturbations are still compatible with most recent data on cosmic microwave background anisotropies and on the shape of the galaxy power spectrum, provided that one allows for a very blue spectrum of primordial entropy fluctuations (n_iso > 2). However, such models predict an excess of matter fluctuations on small scales, typically below 40 Mpc/h. We show that the proper inclusion of high-resolution high signal-to-noise Lyman-alpha forest data excludes most of these models. The upper bound on the isocurvature fraction alpha=f_iso^2/(1+f_iso^2), defined at the pivot scale k_0=0.05/Mpc, is pushed down to alpha<0.4, while n_iso=1.9+-1.0 (95% confidence limits). We also study the bounds on curvaton models characterized by maximal correlation between curvature and isocurvature modes, and a unique spectral tilt for both. We find that f_iso<0.05 (95% c.l.) in that case. For double inflation models with two massive inflatons coupled only gravitationally, the mass ratio should obey R < 3 (95% c.l.).
Beltran Maria
Garcia-Bellido Juan
Lesgourgues Julien
Viel Matteo
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