On the prior dependence of constraints on the tensor-to-scalar ratio
arXiv:1107.2673 · doi:10.1088/1475-7516/2011/09/027
Abstract
We investigate the prior dependence of constraints on cosmic tensor perturbations. Commonly imposed is the strong prior of the single-field inflationary consistency equation, relating the tensor spectral index nT to the tensor-to-scalar ratio r. Dropping it leads to significantly different constraints on nT, with both positive and negative values allowed with comparable likelihood, and substantially increases the upper limit on r on scales k = 0.01 Mpc^-1 to 0.05 Mpc^-1, by a factor of ten or more. Even if the consistency equation is adopted, a uniform prior on r on one scale does not correspond to a uniform one on another; constraints therefore depend on the pivot scale chosen. We assess the size of this effect and determine the optimal scale for constraining the tensor amplitude, both with and without the consistency relation.
14 pages, 6 figures. v2: added references. v3: minor clarifications; added reference; matches version accepted by JCAP
References in corpus (12)
- Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
- Fitting CMB data with cosmic strings and inflation
- Curvature and isocurvature perturbations from two-field inflation in a slow-roll expansion
- Constraints on Supersymmetric Models of Hybrid Inflation
- On what scale should inflationary observables be constrained?
- Constraints on the Inflationary Expansion from Three Year WMAP, small scale CMB anisotropies and Large Scale Structure Data Sets
- Detecting relic gravitational waves in the CMB: Optimal parameters and their constraints
- The consistency equation hierarchy in single-field inflation models
- Is Cosmology Compatible with Blue Gravity Waves ?
- Detecting Relic Gravitational Waves in the CMB: Comparison of Planck and Ground-based Experiments
- Detection of relic gravitational waves in the CMB: Prospects for CMBPol mission
- Are all perturbations created equal? An analysis of the WMAP 5- and 7-year data without inflationary prejudice