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The large scale CMB cut-off and the tensor-to-scalar ratio

Gavin Nicholson·Carlo R. Contaldi
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Abstract

We show that if inflation lasted just longer than the required 60 or so e-folds $N$ both scalar and tensor contributions to the Cosmic Microwave Background (CMB) power spectra are expected to show a cut-off. However the behaviour of the scalar-to-tensor ratio on large scale depends on whether inflation is preceded by a Kinetic Dominated (KD) or Radiation Dominated (RD) stage. Future experiments may be able to distinguish between the two behaviours and thus shed light on the nature of the low-$\ell$ cutoff. In particular if the cut-off is due to a KD stage the ratio is expected to grow on large scales. If observed this would challenge our current understanding of the overall probability of inflation lasting for $N$ greater than 60.

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Gavin Nicholson, Carlo R. Contaldi. 2008-01-16. The large scale CMB cut-off and the tensor-to-scalar ratio. https://doi.org/10.1088/1475-7516%2F2008%2F01%2F002

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