Are primordial black holes produced by entropy perturbations in single field inflationary models?. (arXiv:1904.07503v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Vallejo_Pena_S/0/1/0/all/0/1">Sergio Andrés Vallejo-Peña</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Romano_A/0/1/0/all/0/1">Antonio Enea Romano</a>
We show that in single field inflationary models the super-horizon evolution
of curvature perturbations on comoving slices $mathcal{R}$, which can cause
the production of primordial black holes (PBH), is not due to entropy
perturbations but to a fast variation of the equation of state $w$. As an
example we analyze curvature and entropy perturbations in quasi-inflection
inflation, showing that while entropy perturbations are decreasing,
$mathcal{R}$ can grow on super-horizon scales. This happens in the time
interval during which a sufficiently fast decrease of $w$ transforms into a
growing mode what in slow-roll models would be a decaying mode. The same
mechanism also explains the super-horizon evolution of $mathcal{R}$ in
globally adiabatic systems such as ultra slow roll inflation and its
generalizations.
We show that in single field inflationary models the super-horizon evolution
of curvature perturbations on comoving slices $mathcal{R}$, which can cause
the production of primordial black holes (PBH), is not due to entropy
perturbations but to a fast variation of the equation of state $w$. As an
example we analyze curvature and entropy perturbations in quasi-inflection
inflation, showing that while entropy perturbations are decreasing,
$mathcal{R}$ can grow on super-horizon scales. This happens in the time
interval during which a sufficiently fast decrease of $w$ transforms into a
growing mode what in slow-roll models would be a decaying mode. The same
mechanism also explains the super-horizon evolution of $mathcal{R}$ in
globally adiabatic systems such as ultra slow roll inflation and its
generalizations.
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