Observational constraints on the spectral index of the cosmological curvature perturbation

Abstract

We evaluate the observational constraints on the spectral index $n$, in the context of the $\Lambda$CDM hypothesis which represents the simplest viable cosmology. We first take $n$ to be practically scale-independent. Ignoring reionization, we find at a nominal 2-$\sigma$ level $n\simeq 1.0\pm 0.1$. If we make the more realisitic assumption that reionization occurs when a fraction $f\sim 10^{-5}$ to 1 of the matter has collapsed, the 2-$\sigma$ lower bound is unchanged while the 1-$\sigma$ bound rises slightly. These constraints are compared with the prediction of various inflation models. Then we investigate the two-parameter scale-dependent spectral index, predicted by running-mass inflation models, and find that present data allow significant scale-dependence of $n$, which occurs in a physically reasonable regime of parameter space.

ReVTeX, 15 pages, 5 figures and 3 tables, uses epsf.sty Improved treatment of reionization and small bug fixed in the constant n case; more convenient parameterization and better treatment of the n dependence in the CMB anisotropy for the running mass case; conclusions basically unchanged; references added

References in corpus (8)

• A Flat Universe from High-Resolution Maps of the Cosmic Microwave Background Radiation
• The Cosmic Triangle: Revealing the State of the Universe
• Non-Thermal Production of Dangerous Relics in the Early Universe
• Black hole constraints on the running-mass inflation model
• Constraints on TeV-scale hybrid inflation and comments on non-hybrid alternatives
• Implementing quadratic supergravity inflation
• Late-time creation of gravitinos from the vacuum
• The abundance of moduli, modulini and gravitinos produced by the vacuum fluctuation

Cited by in corpus (19)

• Observable Spectra of Induced Gravitational Waves from Inflation
• Observable induced gravitational waves from an early matter phase
• Models of inflation liberated by the curvaton hypothesis
• Black hole formation and slow-roll inflation
• WMAPping inflationary physics
• Generating Primordial Black Holes Via Hilltop-Type Inflation Models
• New Constraints on inflation from the Cosmic Microwave Background
• Scale Dependent Spectral Index in Slow Roll Inflation
• Precise Measurements of Primordial Power Spectrum with 21 cm Fluctuations
• How to fool CMB parameter estimation
• The running-mass inflation model and WMAP
• New Constraints on the running-mass inflation model
• Cosmological constraints from evaporations of primordial black holes
• Global fits for the spectral index of the cosmological curvature perturbation
• Cosmological parameters from complementary observations of the Universe
• Chaotic Inflation with Time-Variable Space Dimensions
• CMB and Cosmological Parameters: Current Status and Prospects
• Cosmology Rounding the Cape
• Multiple Peaks in the CMB