The problem has frustrated scientists working in cosmology, since almost any modification to the BBN theory that corrects the lithium abundance inadvertently throws off the hydrogen or helium abundances, or contradicts other constraints on the theory. The situation may be compared to trying to solve a Rubik's cube that has only one square of the wrong color.
Now in a new paper published in Physical Review Letters, physicists Vivian Poulin and Pasquale Dario Serpico at Université Savoie Mont Blanc, CNRS, in Annecy-le-Vieux, France, have suggested that the lithium problem may be connected to an overlooked loophole in another theory: that of electromagnetic cascades. Although addressing the lithium problem is not the main result of the paper, it illustrates the potential impact of these broader findings.
"The general result we found in our paper is not specifically related to the lithium problem, rather to the inaccuracy of an approximation used to describe perfectly standard physics, related to cascades," Serpico told Phys.org.
An electromagnetic cascade refers to the cascade of particles produced from a collision between photons and/or electrons. Such a collision results in a chain of reactions in which energy is redistributed among larger numbers of particles, where the energy per particle decreases.
The standard theory of electromagnetic cascades describes this redistribution of energy by predicting a specific shape of the spectrum of photon energies in the cascade. Many different areas of research, including BBN theory, have used this spectral shape when developing models of various phenomena, such as the production of the light elements.
Here, Poulin and Serpico show that, in some cases, this distribution of energy should be computed differently. They point to a previously known but often-overlooked exception to this spectral shape: when the energy of the colliding photon falls below a certain level, the spectral shape deviates from the normal predicted shape. This change could have many consequences, one of which concerns the lithium problem.
"More high-energy photons are present in the correctly computed spectrum than in the approximation typically used in the literature," Poulin said. Phys.org
And though I have the gift of prophecy,
and understand all mysteries,
and all knowledge;
and though I have all faith,
so that I could remove mountains,
and have not LOVE, I am nothing.
1 Corinthians 13:2