Strongly Coupled Dark Energy Cosmologies yielding large mass Primordial Black Holes

TL;DR

This paper explores how strongly coupled dark energy models can facilitate the formation of large primordial black holes, potentially addressing cosmological fine-tuning issues and providing seeds for supermassive black holes.

Contribution

It demonstrates that specific parameter choices in SCDEW models can produce large primordial black holes and align closely with $ ext{Lambda}$CDM, offering a novel mechanism for early universe structure formation.

Findings

PBH masses depend on the Higgs-scale mass $m_H$ and coupling $eta$.

SCDEW models can produce PBHs with masses up to $10^8 M_ ext{sun}$.

Minor discrepancies from $ ext{Lambda}$CDM at high $k$ scales, diminishing with larger $m_H$.

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.