Primordial black hole formation from the merger of oscillons

Abstract

We show that the merger of oscillons results in a broad spectrum of the oscillon mass. A huge number of oscillon samples obtained from numerical lattice simulations reveal that the oscillon mass distribution has an exponential tail in a heavy-mass region. This enables us to infer the fractional abundance of heavy oscillons. Using the criterion for the primordial black hole (PBH) formation from the oscillon collapse obtained in previous studies, we estimate the abundance of PBHs and conclude that a sizable number of PBHs can be produced from oscillons. It can be an alternative PBH formation mechanism without employing the tuning of the inflaton potential to enhance the small-scale density fluctuations in the conventional PBH formation scenario.

Figures (3)

• Figure 1: Snapshots of the three oscillon merger process with the time evolving from left to right. The yellow surface corresponds to the density contrast $\delta = 20$. The length of each axis is $96\Delta x$.
• Figure 2: Snapshots of oscillon samples at $t=600m^{-1}$. The yellow surface corresponds to the density contrast $\delta = 500$. The oscillon masses are $mM/M_{\rm pl}^2 = 2.96$, $2.82$, $2.81$ from left to right. We have taken $\Lambda = 0.05M_{\rm pl}$, $\alpha = 0.15$ and $\phi_i = 2 \Lambda$. The length of each axis is $15\Delta x$.
• Figure 3: Histogram of the oscillon mass for $\phi_i = 1.5\Lambda$ (top), $2\Lambda$ (bottom). The different colors show the different time slices from $t=125m^{-1}$ to $600m^{-1}$ with the interval $\Delta t = 25m^{-1}$. For example, the red, green, blue correspond respectively to $mt=125,\,150,\,175$. The thick black line corresponds to the final time $t=600m^{-1}$. The dashed magenta line represents the exponential fitting function (\ref{['eq:fitting']}) with $(A,\,B) = (12,\,12)$ (top) and $(13,\,10)$ (bottom).