Letter to the Editor

Scale-invariant vacuum guided resolution of the ⁷Li BBN problem

¹ Institute for Advanced Physical Studies, Sofia, Bulgaria
² National Coalition of Independent Scholars, Battleboro, VT, USA
³ Ronin Institute for Independent Scholarship 2.0, Sacramento, CA, USA

^⋆ Corresponding author.

Received: 9 July 2025
Accepted: 10 September 2025

Abstract

A possible resolution of the ⁷Li problem within the scenario of the standard model big bang nucleosynthesis (BNN) is presented. The key idea originates from the application of the scale-invariant vacuum (SIV) paradigm to the BBN. However, here we arrive at the conclusion that reparametrization-invariant symmetry scaling (RISS) is the more appropriate framework for the epoch of the BBN and use the SIV only as a guidance framework. The outcome is a χ² < 0.04 fit to the observed primordial abundances of ⁴He, D/H, ³He/D, and a fit of χ² ≈ 1 when including ⁷Li/H observations. The results are obtained and compared to the known standard BBN values by utilizing the publicly available PRIMAT code. The resolution of the ⁷Li problem requires a SIV-guided deviation from the local thermal equilibrium during BBN, such that the thermal energy of matter and radiation scale differently with respect to the SIV-conformal factor λ during the BBN epoch. This may be viewed as conformal symmetry breaking due to cooling of plasma and the properties of matter, which means that the framework may be of relevance to the problem of nuclear fusion as well. The deduced baryon matter content is Ω_b ≈ 12% for unbroken SIV and Ω_b ≈ 38% for partially broken SIV, but with λ < 1 in both cases, which signals preference for RISS over the conventional SIV viewpoint. Applying the RISS paradigm results in λ > 1 and Ω_b ≈ 10% with a clear departure of n_T from the naive SIV suggested value. In all the cases where the ⁷Li problem is resolved, the baryon content is significantly higher than the usually accepted value of Ω_b ≈ 4.9% within the Lambda cold dark matter (ΛCDM) model.