Big Bang nucleosynthesis in a weakly non-ideal plasma

¹ Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 61005, Republic of Korea
² Research Institute of Basic Science, Korea Aerospace University, Goyang 10540, Republic of Korea
e-mail: ykwon@kau.ac.kr
³ Center for Extreme Nuclear Matters (CENuM), Korea University, Seoul 02841, Republic of Korea
⁴ Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
⁵ Department of Physics and OMEG Institute, Soongsil University, Seoul 06978, Republic of Korea

Received: 22 May 2020
Accepted: 28 March 2021

Abstract

We propose a correction of the standard Big Bang nucleosynthesis (BBN) scenario to resolve the primordial lithium problem by considering a possibility that the primordial plasma can deviate from the ideal state. In the standard BBN, the primordial plasma is assumed to be ideal, with particles and photons satisfying the Maxwell-Boltzmann and Planck distribution, respectively. We suggest that this assumption of the primordial plasma being ideal might oversimplify the early Universe and cause the lithium problem. We find that a deviation of photon distribution from the Planck distribution, which is parameterised with the help of Tsallis statistics, can resolve the primordial lithium problem when the particle distributions of the primordial plasma still follow the Maxwell-Boltzmann distribution. We discuss how the primordial plasma can be weakly non-ideal in this specific fashion and its effects on the cosmic evolution.