Self-consistent strong screening applied to thermonuclear reactions

Abstract: Self-consistent strong plasma screening around light nuclei is implemented in the Big Bang nucleosynthesis (BBN) epoch to determine the short-range screening potential, $e\phi(r)/T \geq 1$, relevant for thermonuclear reactions. We numerically solve the non-linear Poisson-Boltzmann equation incorporating Fermi-Dirac statistics adopting a generalized screening mass to find the electric potential in the cosmic BBN electron-positron plasma for finite-sized $^4$He nuclei as an example. Although the plasma follows Boltzmann statistics at large distances, Fermi-Dirac statistics is necessary when work performed by ions on electrons is comparable to their rest mass energy. While strong screening effects are generally minor due to the high BBN temperatures, they can enhance the fusion rates of high-$Z>2$ elements while leaving fusion rates of lower-$Z\le 2$ elements relatively unaffected. Our results also reveal a pronounced spatial dependence of the strong screening potential near the nuclear surface. These findings about the electron-positron plasma's role refine BBN theory predictions and offer broader applications for studying weakly coupled plasmas in diverse cosmic and laboratory settings.