Constraints on Models with a Break in the Primordial Power Spectrum

TL;DR

This paper investigates how current cosmological observations constrain models with a break in the primordial power spectrum, particularly those motivated by the matter bounce scenario, using extensive data sets and MCMC analysis.

Contribution

It provides the first comprehensive constraints on the location and slope of a spectral break in the primordial power spectrum based on multiple cosmological data sets.

Findings

Upper limit on the scale of the spectral break.

Constraints on the slope change at small scales.

Compatibility of the matter bounce model with current data.

Abstract

One of the characteristics of the "Matter Bounce" scenario, an alternative to cosmological inflation for producing a scale-invariant spectrum of primordial adiabatic fluctuations on large scales, is a break in the power spectrum at a characteristic scale, below which the spectral index changes from n = 1 to n = 3. We study the constraints which current cosmological data place on the location of such a break, and more generally on the position of the break and the slope at length scales smaller than the break. The observational data we use include the WMAP five-year data set (WMAP5), other CMB data from BOOMERanG, CBI, VSA, and ACBAR, large-scale structure data from the Sloan Digital Sky Survey (SDSS, their luminous red galaxies sample), Type Ia Supernovae data (the "Union" compilation), and the Sloan Digital Sky Survey Lyman-\alpha forest power spectrum (Ly\alpha) data. We employ the Markov Chain Monte Carlo method to constrain the features in the primordial power spectrum which are motivated by the matter bounce model. We give an upper limit on the length scale where the break in the spectrum occurs.