Cosmological lithium problem: Difference between revisions

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{{short description|Discrepancy between the observed abundance of lithium produced in Big Bang nucleosynthesis and the amount that should theoretically exist.}}

In [[astronomy]], the '''lithium problem''' or '''lithium discrepancy''' refers to the discrepancy between the primordial [[Abundance of the chemical elements|abundance]] of [[lithium]] as inferred from observations of metal-poor ([[Stellar population|Population II]]) [[Stellar halo|halo stars]] in our Galaxygalaxy and the amount that should theoretically exist due to [[Big Bang nucleosynthesis]]+[[Wilkinson Microwave Anisotropy Probe|WMAP]] cosmic baryon density predictions of the [[Cosmic microwave background|CMB]]. Namely, the most widely accepted models of the Big Bang suggest that three times as much primordial lithium, in particular [[lithium-7]], should exist. This contrasts with the observed abundance of isotopes of [[hydrogen]] (¹H and [[deuterium|²H]]) and [[helium]] ([[helium-3|³He]] and [[helium-4|⁴He]]) that are consistent with predictions.<ref name=HouStats>{{cite journal |last=Hou |first=S. Q. |last2=He |first2=J.J. |last3=Parikh |first3=A. |last4=Kahl |first4=D. |last5=Bertulani |first5=C.A. |last6=Kajino |first6=T. |last7=Mathews |first7=G.J. |last8=Zhao |first8=G. |date=2017 |title=Non-extensive statistics to the cosmological lithium problem |journal=The Astrophysical Journal |volume=834 |issue=2 |pages= 165|doi=10.3847/1538-4357/834/2/165 |bibcode=2017ApJ...834..165H |arxiv=1701.04149 }}</ref> The discrepancy is highlighted in a so-called "Schramm plot", named in honor of astrophysicist [[David Schramm (astrophysicist)|David Schramm]], which depicts these primordial abundances as a function of cosmic baryon content from standard [[Big Bang nucleosynthesis|BBN]] predictions.

[[File:Schramm plot BBN review 2019.png|thumb|400px|This "Schramm plot"<ref>{{cite journal | last=Tanabashi | first=M. | last2=Hagiwara | first2=K. | last3=Hikasa | first3=K. | last4=Nakamura | first4=K. | last5=Sumino | first5=Y. | last6=Takahashi | first6=F. | last7=Tanaka | first7=J. | last8=Agashe | first8=K. | last9=Aielli | first9=G. | last10=Amsler | first10=C. | display-authors=5|collaboration=Particle Data Group| title=Review of Particle Physics | journal=Physical Review D | publisher=American Physical Society (APS) | volume=98 | issue=3 | date=2018-08-17 | issn=2470-0010 | doi=10.1103/physrevd.98.030001 | page=030001|doi-access=free}} and 2019 update.</ref> depicts primordial abundances of ⁴He, D, ³He, and ⁷Li as a function of cosmic baryon content from standard BBN predictions. CMB predictions of 7Li (narrow vertical bands, at 95% [[confidence level|CL]]) and the BBN D&nbsp;+&nbsp;⁴He concordance range (wider vertical bands, at 95% CL) should overlap with the observed light element abundances (yellow boxes) to be in agreement. This occurs in ⁴He and is well constrained in D, but is not the case for ⁷Li, where the observed Li observations lie a factor of 3−4 below the BBN+WMAP prediction.]]