Primordial black holes from the preheating instability in single-field inflation

Abstract

After the end of inflation, the inflaton field oscillates around a local minimum of its potential and decays into ordinary matter. These oscillations trigger a resonant instability for cosmological perturbations with wavelengths that exit the Hubble radius close to the end of inflation. In this paper, we study the formation of Primordial Black Holes (PBHs) at these enhanced scales. We find that the production mechanism can be so efficient that PBHs subsequently dominate the content of the universe and reheating proceeds from their evaporation. Observational constraints on the PBH abundance also restrict the duration of the resonant instability phase, leading to tight limits on the reheating temperature that we derive. We conclude that the production of PBHs during reheating is a generic and inevitable property of the simplest inflationary models, and does not require any fine tuning of the inflationary potential.

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

“…The processes and time-scales over which such distributions of particles relax into thermal equilibrium remain much less understood, and an important area for further research; progress may be made by exploiting methods developed for the study of other systems, such as quark-gluon plasma in the context of heavy ion collisions [188]. Another interesting area of research concerns incorporating gravitational effects more fully into our understanding of post-inflation reheating [189,190,191,192,193,194,195,196,131,197,185].…”

“…Requiring that the Universe transitions to RD epoch prior to BBN implies an upper mass bound on the PBHs, around 6 × 10 5 kg [307]. Additionally, it was recently pointed out that PBHs could be very efficiently produced from the preheating instability so that they dominate the energy density of the Universe, and therefore the reheating no longer occurs because of inflaton decays, but rather due to evaporation of the PBHs [197,308]. PBHs are discussed further in Sec.…”

“…Actually, so far a lot of inflationary models have been proposed in which PBHs are produced at small scales while simultaneously fitting the CMB normalization at large scales. For example, there are models of double inflation [920,887], hilltop inflation [921,922,923], preheating [924,197], curvaton [925,213], thermal inflation [250], false vacuum bubbles [926,927], Q-ball formation [91,928], and so on. These models predict that curvature perturbation can be P ζ ∼ O(0.1) at small scales due to special features in the spectrum, e.g.…”

Seeding Primordial Black Holes in Multifield Inflation

“…Such an amplification can be achieved in several ways. Examples include: single-field models with special potentials [16][17][18][19][20][21][22]; single-field models with resonant backgrounds [23,24]; models with light spectator fields [25][26][27][28]; models where the inflaton couples to gauge fields [29,30]; models with resonant instabilities during the preheating inflaton's decay [31][32][33]. In this work, we are particularly interested in reexamining the enhancement of Δ ζ ðkÞ within the paradigm of multifield inflation [34][35][36][37][38].…”

Mass bound for primordial black hole from trans-Planckian censorship conjecture

“…We conclude in the last section. It is worth noting that, the derived PBH mass bounds would not be applicable to other scenarios of PBH production from curvaton [25,26], scalar lumps [27,28], cosmic strings [29,30], domain walls [31,32], primordial bubbles [33], bubble collisions [34,35], and preheating instability [36], to name just a few.…”