1999/04/18 by J. P. Zibin, D. Scott, Douglas Scott +5
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics (astro-ph) #Cosmology and Gravitation Theories #FOS: Physical sciences #Geophysics and Gravity Measurements #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9904228
5 pages, 1 figure, Gravity Research Foundation essay
arxiv created 1999/04/18 · openalex publication_date 1999/04/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The detection of a stochastic background of long-wavelength gravitational waves (tensors) in the cosmic microwave background (CMB) anisotropy would be an invaluable probe of the high energy physics of the early universe. Unfortunately a combination of factors now makes such a detection seem unlikely: the vast majority of the CMB signal appears to come from density perturbations (scalars) - detailed fits to current observations indicate a tensor-to-scalar quadrupole ratio of T/S < 0.5 for the simplest models; and on the theoretical side the best-motivated inflationary models seem to require very small T/S. Unfortunately CMB temperature anisotropies can only probe a gravity wave signal down to T/S ∼ 10% and optimistic assumptions about polarization of the CMB only lower this another order of magnitude.