Updated constraints and forecasts on primordial tensor modes

2015/11/30 by Giovanni Cabass, L. Pagano, Luca Pagano +7
Physics and Astronomy · #Anisotropy #Astrophysics #Black Holes and Theoretical Physics #Cosmic microwave background #Cosmology and Gravitation Theories #Geometry #Gravitational wave #Physics #Planck #Pulsar #Pulsars and Gravitational Waves Research #Quantum mechanics #Scalar (mathematics) #Spectral density #Statistics #Tensor (intrinsic definition) #astro-ph.CO #hep-ph

paper · pdf · doi:10.1103/physrevd.93.063508

published as Phys. Rev. D 93, 063508 (2016) · 12 + 7 pages, 6 figures, 6 tables. Matches published version

arxiv created 2016/03/03 · openalex publication_date 2016/03/11 · arxiv updated 2016/03/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

We present new, tight, constraints on the cosmological background of gravitational waves (GWs) using the latest measurements of CMB temperature and polarization anisotropies provided by the Planck, BICEP2 and Keck Array experiments. These constraints are further improved when the GW contribution N_eff^GW to the effective number of relativistic degrees of freedom N_eff is also considered. Parametrizing the tensor spectrum as a power law with tensor-to-scalar ratio r, tilt n_t and pivot 0.01 Mpc^\ensuremath-1, and assuming a minimum value of r=0.001, we find r<0.089, n_t=1.7_\ensuremath-2.0^+2.1 (95% CL, no N_eff^GW) and r<0.082, n_t=\ensuremath-0.05_\ensuremath-0.87^+0.58 (95% CL, with N_eff^GW). When the recently released 95 GHz data from Keck Array are added to the analysis, the constraints on r are improved to r<0.067 (95% CL, no N_eff^GW), r<0.061 (95% CL, with N_eff^GW). We discuss the limits coming from direct detection experiments such as LIGO-Virgo, pulsar timing (European Pulsar Timing Array) and CMB spectral distortions (FIRAS). Finally, we show future constraints achievable from a COrE-like mission: if the tensor-to-scalar ratio is of order 10^\ensuremath-2 and the inflationary consistency relation n_t=\ensuremath-r/8 holds, COrE will be able to constrain n_t with an error of 0.16 at 95% CL. In the case that lensing B-modes can be subtracted to 10% of their power, a feasible goal for COrE, these limits will be improved to 0.11 at (95% CL).

Citations

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