A Dual Solution to the Cosmological Lithium Problem and Early Supermassive Black Hole Origins via Direct Collapse Photodisintegration

A Dual Solution to the Cosmological Lithium Problem and Early Supermassive Black Hole Origins via Direct Collapse Photodisintegration Author: Masaki Tsuchimoto Date: January 7, 2026 Subject: Theoretical Astrophysics / Cosmology Abstract Standard Big Bang Nucleosynthesis (BBN) accurately predicts the primordial abundances of light elements except for Lithium-7, which is observed at approximately one-third of its theoretical value (the "Cosmological Lithium Problem"). Simultaneously, the presence of supermassive black holes (SMBHs) at high redshifts (z > 6) challenges current growth models. We propose a unified solution: the formation of Direct Collapse Black Holes (DCBHs) in the early universe. In this model, the intense gamma-ray radiation emitted during the rapid formation and accretion of DCBHs triggers the photodisintegration of nearby Lithium-7 and its parent Beryllium-7. This mechanism selectively reduces lithium abundance in localized primordial gas clouds from which the first metal-poor stars formed, while providing the necessary "seeds" for early SMBHs. 1. Introduction The Cosmological Lithium Problem remains one of the most significant discrepancies in the standard Lambda-CDM model. While the predicted abundances for Hydrogen and Helium match observations with high precision, the primordial Lithium-7 abundance measured in the "Spite Plateau" of metal-poor halo stars is significantly lower than BBN predictions. Concurrently, the "Early Quasar Problem" reveals SMBHs exceeding 10^9 M_\odot within the first billion years of cosmic history. Seed models based on stellar-mass black holes require unrealistic accretion rates, leading to the growing consensus around the Direct Collapse (DCBH) scenario. This paper explores the radiological impact of these DCBH events on the surrounding primordial chemistry. 2. The DCBH Photodisintegration Mechanism 2.1. Seed Formation and High-Energy Emission Under the DCBH scenario, massive gas clouds (10^4 - 10^6 M_\odot) collapse directly into a black hole without the intermediate star-formation phase. This catastrophic gravitational collapse and subsequent hyper-accretion generate intense electromagnetic radiation, particularly in the gamma-ray and hard X-ray spectrum. 2.2. Selective Nuclear Destruction Lithium-7 and Beryllium-7 have relatively low nuclear binding energies compared to Helium-4. High-energy photons emitted by DCBHs can exceed the threshold for (\gamma, n) or (\gamma, p) reactions: * ^7\text{Li} + \gamma \rightarrow ^6\text{Li} + n or ^3\text{H} + ^4\text{He} * This process, termed "Primordial Photodisintegration," occurs within the vicinity of the DCBH seed formation. Because ^4\text{He} has a much higher binding energy, it remains unaffected, preserving the successful Helium predictions of BBN while specifically depleting the Lithium/Beryllium isotopes. 3. Observational Implications The localized nature of DCBH formation creates a non-homogeneous distribution of lithium-depleted gas. The Population II stars we observe today in the galactic halo likely formed from these specific pockets of gas that were "sterilized" by DCBH radiation. This explains why the observed Lithium-7 abundance is consistently low across the Spite Plateau, despite the high predictions of BBN. 4. Conclusion By identifying the radiological byproduct of Direct Collapse Black Hole formation, we provide a self-consistent physical explanation for the missing primordial Lithium-7. This model eliminates the need for exotic new physics or a fundamental revision of the Big Bang Nucleosynthesis OS, instead suggesting that the "Lithium Gap" is a relic of the very events that seeded the massive structures of our current universe.