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arXiv · 2111.06794

Cuscuton Inflation

Nicola Bartolo·Alexander Ganz·Sabino Matarrese
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Abstract

We study the impact of (generalized) cuscuton models on standard single scalar field inflation. Generalized cuscuton models are characterized by spatial covariant gravity where a scalar degree of freedom is made non dynamical, and there are just two tensor degrees of freedom. The presence of the non-dynamical scalar field does not spoil inflation but instead the modifications are, in general, slow-roll suppressed leading to almost scale-invariant power spectra. However, the extra free parameters, which can be tuned relatively independently, lead to a larger parameter range for observable quantities, such as the tensor-to-scalar ratio. For the (generalized) cuscuton model the non-Gaussianties of the curvature bispectrum are suppressed by the slow-roll parameters, and, therefore, outside the reach of current experiments. However, generalized cuscuton models can lead to a different shape for the bispectrum which might be constrained by future experiments.

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Nicola Bartolo, Alexander Ganz, Sabino Matarrese. 2022-05-09. Cuscuton Inflation. https://doi.org/10.1088/1475-7516%2F2022%2F05%2F008

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