Non-Gaussian signatures of Tachyacoustic Cosmology

Abstract

I investigate non-Gaussian signatures in the context of tachyacoustic cosmology, that is, a noninflationary model with superluminal speed of sound. I calculate the full non-Gaussian amplitude $\mathcal{A}$, its size $f_{\mathrm{NL}}$, and corresponding shapes for a red-tilted spectrum of primordial scalar perturbations. Specifically, for cuscuton-like models I show that $f_{\mathrm{NL}}\sim \mathcal{O}(1)$, and the shape of its non-Gaussian amplitude peaks for both equilateral and local configurations, the latter being dominant. These results, albeit similar, are quantitatively distinct from the corresponding ones obtained by Magueijo {\it{et. al}} in the context of superluminal bimetric models.

Some comments and references added. Matches the version published in JCAP

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• Consistency of Tachyacoustic Cosmology with de Sitter Swampland Conjectures
• Attractor Solutions in Tachyacoustic Cosmology