Strongly Coupled Dark Energy Cosmologies yielding large mass Primordial Black Holes

Abstract

Large primordial Black Hole (PBH) formation is enhanced if strongly coupled scalar and spinor fields ($\Phi$ and $\psi$) are a stable cosmic component since the primeval radiative expansion (SCDEW models). In particular, we show that PBH formation is easier at a specific time, i.e., when the asymptotic mass $m_H$, acquired by the $\psi$ field at the higgs scale, becomes dominant, so that the typical BH mass $M_{BH}$ depends on $m_H$ value. For instance, if $m_H \sim 100\,$ eV $(1$ keV$)$ and the coupling $\beta \sim 8.35 (37)$, PBH with $M_{BH} \simeq 10^7-10^8 $ $(10^3-10^4)\, M_\odot$ could form. The very mechanism enhancing PBH formation also causes technical difficulties to evaluate the transfer function of SCDEW models at high $k$. A tentative solution of this problem leaves only minor discrepancies from $\Lambda$CDM, also at these scales, gradually vanishing for greater $m_H$ values. We conclude that, for suitable parameter choices, SCDEW models could be the real physics underlying $\Lambda$ CDM, so overcoming its fine tuning and coincidence problems, with the extra bonus of yielding large BH seeds.