Tensors, BICEP2, prior dependence, and dust

Abstract

We investigate the prior dependence on the inferred spectrum of primordial tensor perturbations, in light of recent results from BICEP2 and taking into account a possible dust contribution to polarized anisotropies. We highlight an optimized parameterization of the tensor power spectrum, and adoption of a logarithmic prior on its amplitude $A_T$, leading to results that transform more evenly under change of pivot scale. In the absence of foregrounds the tension between the results of BICEP2 and Planck drives the tensor spectral index $n_T$ to be blue-tilted in a joint analysis, which would be in contradiction to the standard inflation prediction ($n_T<0$). When foregrounds are accounted for, the BICEP2 results no longer require non-standard inflationary parameter regions. We present limits on primordial $A_T$ and $n_T$, adopting foreground scenarios put forward by Mortonson & Seljak and motivated by Planck 353 GHz observations, and assess what dust contribution leaves a detectable cosmological signal. We find that if there is sufficient dust for the signal to be compatible with standard inflation, then the primordial signal is too weak to be robustly detected by BICEP2 if Planck+WMAP upper limits from temperature and E-mode polarization are correct.

10 pages, 9 figures. v3, minor update to match journal accepted version

References in corpus (20)

• BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales
• Toward an Understanding of Foreground Emission in the BICEP2 Region
• A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty
• Blue Tensor Spectrum from Particle Production during Inflation
• Blue-tilted Tensor Spectrum and Thermal History of the Universe
• Non-Bunch-Davies Initial State Reconciles Chaotic Models with BICEP and Planck
• The gravitational wave background from super-inflation in Loop Quantum Cosmology
• On what scale should inflationary observables be constrained?
• Compatibility of Planck and BICEP2 in the Light of Inflation
• The Knotted Sky II: Does BICEP2 require a nontrivial primordial power spectrum?
• Steps to Reconcile Inflationary Tensor and Scalar Spectra
• Reconstruction of the primordial power spectra with Planck and BICEP2
• Inflation and Alternatives with Blue Tensor Spectra
• Testing quantum gravity effects with latest CMB observations
• On quantifying and resolving the BICEP2/Planck tension over gravitational waves
• Blue Gravity Waves from BICEP2 ?
• Single field inflation with modulated potential in light of the Planck and BICEP2
• Genus Topology and Cross-Correlation of BICEP2 and Planck 353 GHz B-Modes: Further Evidence Favoring Gravity Wave Detection
• The Tilt of Primordial Gravitational Waves Spectra from BICEP2
• Constraints on the cosmological parameters from BICEP2, Planck and WMAP

Cited by in corpus (10)

• Gravitational-wave cosmology across 29 decades in frequency
• Gravitational Waves and Scalar Perturbations from Spectator Fields
• Two-Field Analysis of No-Scale Supergravity Inflation
• Gravity Waves From Non-Minimal Quadratic Inflation
• Reconciling Induced-Gravity Inflation in Supergravity With The Planck 2013 & BICEP2 Results
• Gravitational Waves from Double Hybrid Inflation
• Running of scalar spectral index in multi-field inflation
• Primordial magnetic fields in the $f^{2}FF$ model in large field inflation under de Sitter and power law expansion
• The Primordial Magnetic Field (PMF) Generated in Large Field Inflation (LFI), Natural Inflation (NI) and $R^2$-Inflation by $f^{2}FF$ Model
• Double hybrid inflation and gravitational waves