Observational Constraints on Theories with a Blue Spectrum of Tensor Modes

Abstract

Motivated by the string gas cosmological model, which predicts a blue tilt of the primordial gravitational wave spectrum, we examine the constraints imposed by current and planned observations on a blue tilted tensor spectrum. Starting from an expression for the primordial gravitational wave spectrum normalized using cosmic microwave background observations, pulsar timing, direct detection and nucleosynthesis bounds are examined. If we assume a tensor to scalar ratio on scales of the CMB which equals the current observational upper bound, we obtain from these current observations constraints on the tensor spectral index of $n_T\lesssim 0.79$, $n_T\lesssim 0.53$, and $n_T\lesssim 0.15$ respectively.

12 pages, 1 figure, 2 references added, relationship of this work with Ref. 20 added

References in corpus (4)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Temperature Analysis
• Upper bounds on the low-frequency stochastic gravitational wave background from pulsar timing observations: current limits and future prospects
• Prospects for direct detection of primordial gravitational waves

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