Correlated perturbations from inflation and the cosmic microwave background

TL;DR

It is found that there is a degeneracy between the amplitude of correlated isocurvature perturbations and the spectral tilt, and estimates of the baryon and CDM densities are found to be almost independent of the isocURvature amplitude.

Abstract

We compare the latest cosmic microwave background data with theoretical predictions including correlated adiabatic and CDM isocurvature perturbations with a simple power-law dependence. We find that there is a degeneracy between the amplitude of correlated isocurvature perturbations and the spectral tilt. A negative (red) tilt is found to be compatible with a larger isocurvature contribution. Estimates of the baryon and CDM densities are found to be almost independent of the isocurvature amplitude. The main result is that current microwave background data do not exclude a dominant contribution from CDM isocurvature fluctuations on large scales.

Figures (3)

• Figure 1: Best-fit spectrum (solid line) and the component spectra, shown with the data with one sigma error bars, using maximum-likelihood normalisation and unadjusted relative calibration.
• Figure 2: Contour plot of the two-dimensional likelihood for $B$ and ${\rm cos}\Delta$. The contours enclose 40%, 86% and 99% of the likelihood and the star marks the peak.
• Figure 3: One-dimensional likelihood functions in arbitrary units. Green (light) dotted lines for the purely adiabatic models ($B=0$); blue short-dashed lines for uncorrelated fluctuations ($\cos\Delta =0$); red (dark) solid lines for correlated fluctuations. See text for further explanation.