Cosmological Constraints on Isocurvature and Tensor Perturbations

TL;DR

This work constrains primordial isocurvature and tensor perturbations using CMB and LSS data within a flat LambdaCDM framework while allowing one isocurvature mode (CI, NID, or NIV) and a tensor component. It analyzes three correlation priors and employs CAMB/CosmoMC to fit WMAP3 and SDSS DR4 LRG data, finding no statistical need for isocurvature and setting upper bounds on isocurvature fractions and the tensor-to-adiabatic ratio r. The authors also apply the constraints to axion and curvaton models, deriving strong limits on the axion decay constant f_a and the inflation scale H_inf, and showing that curvaton scenarios require baryon and CDM production by or after curvaton decay to avoid large isocurvature, while lepton asymmetry remains unconstrained. Overall, the results reinforce the adiabatic paradigm while delineating the viable parameter space for inflationary and particle-physics motivated isocurvature scenarios and guiding future observational tests.

Abstract

We investigate cosmological constraints on primordial isocurvature and tensor perturbations, using recent observations of the cosmic microwave background and the large scale structure. We find that present observations are consistent with purely adiabatic initial conditions for the structure formation under any priors on correlations of isocurvature modes, and upper limits on the contribution of isocurvature and tensor perturbations are presented. We also apply the obtained constraints to some specific theoretical models, axion isocurvature perturbation models and curvaton models, and give some implications for theoretical models.

Figures (8)

• Figure 1: 1-dimensional likelihood distributions for uncorrelated isocurvature models with CI (left), NID (middle) and NIV (right) mode, respectively. In each panel we show the distributions for models without tensor modes using WMAP3 data only (red full), with tensor modes using WMAP3 data only (green dashed), without tensor modes using WMAP3 data combined with SDSS DR4 LRG data (blue dotted), with tensor modes using WMAP3 data combined with SDSS DR4 LRG data (magenta dot-dashed).
• Figure 2: 68 % (full) and 95% (dashed) 2-dimensional constraints on the uncorrelated isocurvature models CI (left), NID (middle) and NIV (left) with tensor modes. We present constraints using WMAP3 data only (green) and combined with SDSS DR4 LRG data.
• Figure 3: 1-dimensional likelihood distributions for totally correlated isocurvature models . Considered isocurvature and tensor modes and combinations of data are same as Figure \ref{['fig:TC_b']}.
• Figure 4: 68 % and 95% 2-dimensional constraints on the totally correlated isocurvature models with tensor modes. Contours are same as Figure \ref{['fig:UC_b-r']}.
• Figure 5: 1-dimensional likelihood distributions for generally correlated isocurvature models with CI (left), NID (middle) and NIV (right) mode. In each panel, we show distributions for models without tensor modes (red full), with tensor modes imposed inflation consistency relations (green dotted) and with tensor modes with fixed spectral index $n_g=1$ (blue dashed).