Investigating the Lithium Imbalance Issue

By Ibtisam AbbasiReviewed by Louis CastelDec 23 2025

The study of the Big Bang and its aftermath has been essential to understanding the origins and evolution of the universe. Within this context, the framework of Big Bang Nucleosynthesis (BBN), which combines principles from cosmology, quantum physics, and particle physics, has served as a powerful tool for exploring the early universe. BBN provides critical insight into the formation of light elements such as helium, lithium, and their isotopes.

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One of the long-standing puzzles in this field is the cosmological lithium problem, also known as lithium discrepancy. This refers to the mismatch between the predicted abundance of the lithium-7 isotope (⁷Li) based on BBN models and the lower levels actually observed in the spectra of ancient stars and cosmic radiation.¹ Specifically, observations show a ⁷Li concentration about three times lower than what BBN predicts. This discrepancy has sparked extensive research aimed at understanding the root of the problem and refining our models of the early universe

Historical and Theoretical Background

The standard BNN concept played a key role in understanding the formation of light nuclei after the occurrence of the Big Bang. The baryon-to-photon ratio (η) has been determined to be the most critical and sole factor affecting the predictions of BNN. The value of η is determined by the analysis of the Cosmic Microwave Background (CMB) radiation, which is measured using the highly sensitive instruments aboard the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck satellites.²

The CMB measurements are a critical baryon density input for nucleosynthesis calculations, which allow for the determination of elemental concentrations that can easily be compared with modern observational data.

The Discrepancy in Lithium

The BNN nucleosynthesis prediction using CMB has proven excellent agreement between the nucleosynthesis prediction and the observational data for Deuterium (D) and Helium (²He). However, the data for Lithium ⁷Li doesn’t match the current data from main-sequence stars.

The BNN calculations with the CMB input from WMAP reveal an innate abundance in (⁷Li/H) concentration estimated to be around η. However, the analysis of metal-poor halo-stars present in the Spite plateau indicates a value of η.³

The 3-4 times difference in the observed and theoretical value, also known commonly as the Lithium Imbalance issue, has been studied by experts all over the world. A basic explanation is the depletion of lithium due to the stellar processes after the Big Bang, while some concepts also make use of the rotational mixing and magnetic effects to explain the reduction in surface Lithium in Population (Pop) η stars. An alternative explanation makes use of the presence of exotic particles that could be pivotal in altering the lithium production during the primordial nucleosynthesis processes after the Big Bang.⁴ All these concepts and explanations are highly complex, opening up new avenues in cosmology and quantum physics.

Quantum and Astrophysical Tools Addressing the Problem

Several spectroscopic and quantum-level instruments are playing a key role in analyzing the lithium abundance. In this regard, the spectroscopic surveys like the Gaia-ESO, the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), the AMBRE Project, and the GALactic Archaeology with HERMES (GALAH) have been crucial for providing high-resolution spectra, allowing the experts to determine the concentration of Lithium isotopes.⁵

The importance of Lithium isotopes for the study of the universe is unmatched, and the Subaru telescope is critical for the detection of Li-isotopes by observing the high-quality spectrum.⁶ Researchers are also utilizing data from the Gaia-ESO Survey (GES) for the identification of the lithium depletion boundary (LDB) in young stars like NGC 2232, proving to be key for the measurement of the age of stars and the study of the cosmos.⁷ Major organizations, such as the telescopes and FEROS instrument at the European Southern Observatory’s (ESO) La Silla Observatory, have proven to be key in the detection of the element lithium in the material ejection of a Nova.⁸ Furthermore, experts are constantly developing highly accurate novel technologies, such as cryogenic detectors with signal amplification, to ensure constant success in the resolution of the cosmological lithium problem.

Recent Advances and Studies

Experts have tried to find completely accurate solutions concerning the cosmological Lithium problem. In this regard, experts expanded the standard BBN model by the integration of gauged baryon minus lepton numbers. This novel concept involving gauged B-L was spontaneously broken down by a scalar with charge six.

The experts have conceptualized the disintegration of gauged baryon minus lepton number to a discrete subgroup leading to an abundance of cosmic string loops. The experts have conceptualized that these cosmic strings are characterized by disintegrated Lithium nuclei in the early universe, which leads to a reduction in the lithium levels inferred from cosmological observations. The experts have further deduced that the cosmic strings can be found via their gravitational effects, which may affect the Cosmic Microwave Background anisotropies.⁹

Nuclear Physics Resonant Destruction for the Lithium Problem

In another study, experts have explored a novel concept involving nuclear physics to present a possible solution to the lithium problem in metal-poor stars. The novel concept focuses on resonant reactions, which explains the reduction in levels by the enhancement in the destruction rate of ⁷Li or its mirror nucleus ⁷Be.

Previous concepts didn’t take other nuclear reactions into account, which may occur due to the presence of other isotopes and charged species. These may include A = 8 compound nucleus, A = 9 compound nucleus, A = 10 compound nucleus, and A = 11 compound nucleus species. Reactions using the A = 7 light nuclides have been exceptional for explaining the destruction reactions, which will be key for resolving the lithium problems. The experts have found that in comparison to the prominent channels of ⁷Be (n, p) ⁷Li and ⁷Li (η, α ) the subdominant destruction channels are also less-constrained. Furthermore, the experts have also put forward the need to explore quantum mechanics, which will allow us to study resonant properties that will be key for understanding the discrepancies in Lithium levels.¹⁰

Implications of the Lithium Imbalance Issues

The lithium problem has been the backbone of scientific and technological progress in astronomy, quantum physics, and cosmology. The errors in Baryon density, and the determination of cross-sections of associated isotopes led to the development of better instruments like the WMAP, which are now an integral part of several space exploration missions.¹¹

The quest for resolution of the Lithium problem has also enabled breakthroughs in nuclear and exotic physics. Scientists are exploring novel avenues concerning particle physics, such as the particle-matter interaction causing variations in velocity distributions from the usual Maxwell-Boltzmann parameter.¹² These innovations are ushering us into a new era of cosmology.

The focus of experts and researchers on the lithium discrepancy issue is constantly yielding novel frameworks and conceptual frameworks for finding a credible solution. The novel frameworks not only resolve the lithium issues but also define Lithium as the core element enabling cosmic computation, unraveling key information ranging from quantum error correction to biological evolution.¹³

The Universe might be decaying faster than expected - read the story here

Further Reading

1. Fields, B. (2011). The Primordial Lithium Problem. Annual Reviews of Nuclear and Particle Science 2011. 1056-8700/97/0610-00. arXiv (Cornell University). doi.org/10.48550/arXiv.1203.3551
2. Nabila Aghanim, Yashar Akrami, Ashdown, M., J. Aumont, Baccigalupi, C., Ballardini, M., Banday, A.J., Barreiro, R.B., Bartolo, N., Basak, S., Battye, R.A., K. Benabed, Bernard, J., Bersanelli, M., Bielewicz, P., Bock, J.J., Bond, J.R., Borrill, J., Bouchet, F.R. and Boulanger, F. (2021). Planck 2018 results. Astronomy and Astrophysics, 652, pp.C4–C4. doi.org/10.1051/0004-6361/201833910e.
3. Fields, B.D. and Olive, K.A. (2022). Implications of the Non-Observation of ${}^{6}{\rm Li}$ in Halo Stars for the Primordial ${}^{7}{\rm Li}$ Problem. arXiv (Cornell University). doi.org/10.48550/arxiv.2204.03167.
4. Miranda, O.D. (2025). The cosmological lithium problem. Astronomy & Astrophysics, 701, p.A164. doi.org/10.1051/0004-6361/202554482.
5. Ding, M.-Y., Shi, J.-R., Yan, H., Li, C.-Q., Gao, Q., Chen, T.-Y., Zhang, J.-H., Liu, S., Xie, X.-J., Tang, Y.-J., Zhou, Z.-M. and Wang, J.-T. (2024). Lithium Abundances from the LAMOST Med-Resolution Survey Data Release 9. arXiv (Cornell University). doi.org/10.48550/arxiv.2403.01815.
6. Elia, A., Inoue, S., Aoki, W. and Ryan, S. (2008). Lithium Isotopic Abundances in Old Stars. ESO astrophysics symposia, pp.9–13. doi.org/10.1007/978-3-540-75485-5_2.
7. Binks, A.S., Jeffries, R.D., Jackson, R.J., Franciosini, E., Sacco, G.G., Bayo, A., Magrini, L., Randich, S., Arancibia-Silva, J., Bergemann, M., Bragaglia, A., Gilmore, G., Gonneau, A., Hourihane, A., Jofré, P., Korn, A.J., Morbidelli, L., Prisinzano, L., Worley, C.C. and Zaggia, S. (2021). The Gaia-ESO survey: a lithium depletion boundary age for NGC 2232. Monthly Notices of the Royal Astronomical Society, [online] 505(1), pp.1280–1292. doi.org/10.1093/mnras/stab1351.
8. European Southern Observatory (ESO) (2015). First Detection of Lithium from an Exploding Star. [online] www.eso.org. Available at: https://www.eso.org/public/news/eso1531/.
9. Koren, S. (2023). Cosmological Lithium Solution from Discrete Gauged B−L. Physical Review Letters. 131(9). doi.org/10.1103/physrevlett.131.091003.
10. Chakraborty,  N.,  Fields, B.D. and Olive, K.A. (2011). Resonant destruction as a possible solution to the cosmological lithium problem. Physical review, 83(6).  doi.org/10.1103/physrevd.83.063006.
11. Cyburt, R.H., Fields, B.D. and Olive, K.A. (2008). An update on the big bang nucleosynthesis prediction for7Li: the problem worsens. Journal of Cosmology and Astroparticle Physics, 2008(11), p.012. doi.org/10.1088/1475-7516/2008/11/012.
12. Mathews, G.J., Kedia, A., N. Sasankan, M. Kusakabe, Luo, Y., T. Kajino, Yamazaki, D., Makki, T. and Eid, M.E. (2020). Cosmological Solutions to the Lithium Problem. arXiv (Cornell University).  doi.org/10.7566/jpscp.31.011033.
13. DeLooze, J. (2025). Computational Consumption: The Lithium Solution. SSRN Electronic Journal.  doi.org/10.2139/ssrn.5355471.

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