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Inflationary predictions for scalar and tensor fluctuations reconsidered

Latham A. Boyle·Paul J. Steinhardt·Neil Turok
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Abstract

We reconsider the predictions of inflation for the spectral index of scalar (energy density) fluctuations (n_s) and the tensor/scalar ratio (r) using a discrete, model-independent measure of the degree of fine-tuning required to obtain a given combination of (n_s, r). We find that, except for cases with numerous unnecessary degrees of fine-tuning, n_s is less than 0.98, measurably different from exact Harrison-Zel'dovich. Furthermore, if n_s \gtrsim 0.95, in accord with current measurements, the tensor/scalar ratio satisfies r \gtrsim 10^{-2}, a range that should be detectable in proposed cosmic microwave background polarization experiments and direct gravitational wave searches.

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Latham A. Boyle, Paul J. Steinhardt, Neil Turok. 2006-03-22. Inflationary predictions for scalar and tensor fluctuations reconsidered. https://doi.org/10.1103/physrevlett.96.111301

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