SIV Guided Resolution of the Lithium-7 BBN Problem
Vesselin G. Gueorguiev
TL;DR
This work tackles the Cosmological Lithium-7 problem within the Standard Model by extending Big-Bang Nucleosynthesis with the Scale-Invariant Vacuum (SIV) framework and adopting the more general Reparametrization Invariant Symmetry Scaling (RISS) during the BBN epoch. The methodology modifies thermonuclear reaction rates and cosmological evolution through a time-dependent conformal factor $\lambda$, with distinct scaling for rest-mass energy ($n_m=+1$) and thermal energy ($n_T=-\tfrac{1}{2}$) under the constraint $n_m-3=4n_T$, and propagates these changes into the PRIMAT code (using a reduced reaction network) to compute light-element abundances. The study finds that certain SIV/RISS configurations can achieve $\chi^2$ values near unity for $^7$Li/H, especially when allowing $n_T\neq n_m$ and $\lambda>1$, though many fits still fail to fully reconcile all abundances with standard $\,\Omega_b\approx4.9\%$; some cases even require $\Omega_b$ around $10$–$12\%$. The results imply that a departure from local thermal equilibrium, as encoded by a nontrivial $\lambda$ scaling and distortion term $\mathscr{S}(T)$, may resolve the $^7$Li discrepancy within a (nearly) Standard Model framework and could have broader implications for early-universe physics and nuclear fusion, while emphasizing the need for cross-validation with other BBN codes.
Abstract
A possible resolution of the $^7$Li problem within the Standard Model Big-Bang Nucleosynthesis 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 $χ^2<0.04$ fit to the observed primordial abundances of $^4$He, D/H, $^3$He/D, and fit of $χ^2\approx1$ when including $^7$Li/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 $^7$Li problem requires 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. As such, the framework may be of relevance to the problem of the nuclear fusion as well. The deduced baryon matter content is $Ω_b\approx12\%$ for unbroken SIV and $Ω_b\approx38\%$ for partially broken SIV, but with $λ<1$ in both cases, which signals preference for Reparametrization Invariant Symmetry Scaling (RISS) over the conventional SIV viewpoint. Applying the RISS paradigm results in $λ>1$ and $Ω_b\approx10\%$ with clear departure of $n_T$ away from the naive SIV suggested value. In all the cases where the $^7$Li problem is resolved, the baryon content is significantly higher than the usually accepted value of $Ω_b\approx4.9\%$ within the $Λ$CDM. \keywords{Cosmology -- Primordial Nucleosynthesis -- dark matter, Reparametrization Invariance, Scale-Invariant Vacuum (SIV)}