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arXiv · 2501.17226

A universal bound on the duration of a kination era

Cem Eröncel·Yann Gouttenoire·Ryosuke Sato·Géraldine Servant·Peera Simakachorn
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Abstract

We show that primordial adiabatic curvature fluctuations generate an instability of the scalar field sourcing a kination era. We demonstrate that the generated higher Fourier modes constitute a radiation-like component dominating over the kination background after about $11$ e-folds of cosmic expansion. Current constraints on the extra number of neutrino flavors $\Delta N_{\rm eff}$ thus imply the observational bound of approximately 10 e-folds, representing the most stringent bound to date on the stiffness of the equation of state of the pre-Big-Bang-Nucleosynthesis universe.

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Cem Eröncel, Yann Gouttenoire, Ryosuke Sato, Géraldine Servant, Peera Simakachorn. 2025-01-28. A universal bound on the duration of a kination era. https://doi.org/10.1103/k7ty-gwjg

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