# Non-extensive Statistics Solution to the Cosmological Lithium Problem

## TL;DR

This paper proposes that using Tsallis non-extensive statistics to model nucleon velocities during Big Bang nucleosynthesis can reconcile the predicted and observed primordial lithium abundances, potentially solving the longstanding lithium problem.

## Contribution

It introduces a novel application of non-extensive statistics to BBN, providing a new parameter range that aligns predictions with observations.

## Key findings

- Excellent agreement with observed abundances for 1.069 ≤ q ≤ 1.082
- Suggests a new physics solution to the lithium problem
- Reconciles theoretical predictions with observational data

## Abstract

Big Bang nucleosynthesis (BBN) theory predicts the abundances of the light elements D, $^3$He, $^4$He and $^7$Li produced in the early universe. The primordial abundances of D and $^4$He inferred from observational data are in good agreement with predictions, however, the BBN theory overestimates the primordial $^7$Li abundance by about a factor of three. This is the so-called "cosmological lithium problem". Solutions to this problem using conventional astrophysics and nuclear physics have not been successful over the past few decades, probably indicating the presence of new physics during the era of BBN. We have investigated the impact on BBN predictions of adopting a generalized distribution to describe the velocities of nucleons in the framework of Tsallis non-extensive statistics. This generalized velocity distribution is characterized by a parameter $q$, and reduces to the usually assumed Maxwell-Boltzmann distribution for $q$ = 1. We find excellent agreement between predicted and observed primordial abundances of D, $^4$He and $^7$Li for $1.069\leq q \leq 1.082$, suggesting a possible new solution to the cosmological lithium problem.