Optimistic estimation on probing primordial gravitational waves with CMB B-mode polarization

Abstract

In the measurements of cosmic microwave background polarizations, three frequency channels are necessary for discriminating the primordial B-modes from the polarized dust and the synchrotron emission. We carry out an optimistic estimate on the sensitivity to the detection of primordial gravitational waves using the cosmic microwave background B-modes only, and explore how to reach the thresholds for the tensor-to-scalar ratio $r$ in the theoretically well-motivated inflation models. For example, Lyth bound implies $r\simeq 2\times 10^{-3}$, a corrected Lyth bound shows $r\simeq 7\times 10^{-4}$, and some typical inflation models gives $r\simeq 4\times 10^{-5}$. Taking into account the up-to-date constraints on $r$, i.e. $r_{0.05}<0.07$ at $95\%$ confidence, we find that the consistency relation $n_t=-r/8$ in the canonical single-field slow-roll inflation cannot be distinguished from the scale invariance, due to the cosmic variance in the power spectrum of cosmic microwave background B-modes. The cosmic variance places an inevitable limit on the measurements of the tensor spectral index, i.e. ${\sigma }_{n_t}\simeq 0.01$ for $2⩽\ell ⩽{\ell }_{\text{max}}=300$.

9 pages, 2 columns, 12 figures, a revised version accepted by MNRAS

References in corpus (34)

• Planck 2015 results. XIII. Cosmological parameters
• Three Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Polarization Analysis
• A Joint Analysis of BICEP2/Keck Array and Planck Data
• BICEP2 / Keck Array VI: Improved Constraints On Cosmology and Foregrounds When Adding 95 GHz Data From Keck Array
• The Quest for B Modes from Inflationary Gravitational Waves
• Toward an Understanding of Foreground Emission in the BICEP2 Region
• Planck intermediate results. XLVII. Planck constraints on reionization history
• Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes
• Gravitational-wave cosmology across 29 decades in frequency
• A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty
• Resilience of the standard predictions for primordial tensor modes
• Robust forecasts on fundamental physics from the foreground-obscured, gravitationally-lensed CMB polarization
• The LiteBIRD Satellite Mission - Sub-Kelvin Instrument
• Exploring Cosmic Origins with CORE: Survey requirements and mission design
• High angular resolution Sunyaev-Zel'dovich observations of MACS J1423.8+2404 with NIKA: Multiwavelength analysis
• Primordial gravity wave fossils and their use in testing inflation
• Updated Constraints and Forecasts on Primordial Tensor Modes
• Planck intermediate results. L. Evidence for spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB $B$-mode analysis
• The Lyth Bound of Inflation with a Tilt
• High-Scale Inflation and the Tensor Tilt
• Multi-wavelength constraints on the inflationary consistency relation
• Inflation model constraints from data released in 2015
• Constraints on the spectral index for the inflation models in string landscape
• Detecting relic gravitational waves in the CMB: Optimal parameters and their constraints
• Forecasting sensitivity on tilt of power spectrum of primordial gravitational waves after Planck satellite
• The present and future of the most favoured inflationary models after $Planck$ 2015
• Probing the statistical properties of CMB $B$-mode polarization through Minkowski Functionals
• Probing the primordial universe with gravitational waves detectors
• Constraint on the primordial gravitational waves from the joint analysis of BICEP2 and Planck HFI 353 GHz dust polarization data
• No evidence for the blue-tilted power spectrum of relic gravitational waves
• Planck intermediate results. XLI. A map of lensing-induced B-modes
• Lyth bound revisited
• The Impact of Primordial Magnetic Fields on Future CMB Bounds on Inflationary Gravitational Waves
• The Superhorizon Test of Future B-mode Experiments

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