Cosmological lithium problem: Difference between revisions

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{{Short description|Problem in astronomy}}

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 galaxy and the amount that should theoretically exist due to [[Big Bang nucleosynthesis]]+[[Wilkinson Microwave Anisotropy Probe|WMAP]] cosmic baryon density predictions of the [[Cosmiccosmic microwave background|CMB]] (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.<ref>{{cite journal |doi=10.1146/annurev-nucl-102010-130445 |title=The Primordial Lithium Problem |date=2011 |last1=Fields |first1=Brian D. |journal=Annual Review of Nuclear and Particle Science |volume=61 |pages=47–68 |arxiv=1203.3551 |bibcode=2011ARNPS..61...47F }}</ref> 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 |last1=Hou |first1=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 |s2cid=568182 |doi-access=free }}</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 | last1=Tanabashi | first1=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| bibcode=2018PhRvD..98c0001T |doi-access=free| hdl=10044/1/68623 | hdl-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.]]

==Origin of lithium==

Minutes after the Big Bang, the universe was made almost entirely of hydrogen and helium, with trace amounts of lithium and beryllium, and negligibly small abundances of all heavier elements.<ref name="habitable"/><ref>{{cite web|url=https://physics.unc.edu/the-cosmological-lithium-problem/|title=Cosmological lithium problem|website=University of North Carolina|date=14 September 2020 }}</ref>

===Lithium synthesis in the Big Bang===

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The amount of lithium generated in the Big Bang can be calculated.<ref>{{cite journal | bibcode= 1985ARA&A..23..319B | title= Big bang nucleosynthesis – Theories and observations | last1= Boesgaard | first1=A. M. | last2= Steigman | first2= G. | volume= 23 |date= 1985 | pages= 319–378 | journal= [[Annual Review of Astronomy and Astrophysics]] |id=A86-14507 04–90 |___location=Palo Alto, CA | doi= 10.1146/annurev.aa.23.090185.001535}}</ref> [[Hydrogen-1]] is the most abundant [[nuclide]], comprising roughly 92% of the atoms in the Universe, with [[helium-4]] second at 8%. Other isotopes including ²H, ³H, ³He, ⁶Li, ⁷Li, and ⁷Be are much rarer; the estimated abundance of primordial lithium is 10⁻¹⁰ relative to hydrogen.<ref name=23bbn>{{cite book |last1=Tanabashi |first1=M. |display-authors=et al. |editor-last1=Fields |editor-first1=B. D. |editor-last2=Molaro |editor-first2=P. |editor-last3=Sarkar |editor-first3=S. |title=The Review |date=2018 |chapter=Big-bang nucleosynthesis |journal=Physical Review D |volume=98 |issue=3 |pages=377–382 |doi=10.1103/PhysRevD.98.030001 |bibcode=2018PhRvD..98c0001T |url=https://pdg.lbl.gov/2019/reviews/rpp2018-rev-bbang-nucleosynthesis.pdf

}}</ref> The calculated abundance and ratio of ¹H and ⁴He is in agreement with data from observations of young stars.<ref name="habitable">{{cite book |isbn=978-0691140063|title=How to Build a Habitable Planet: The Story of Earth from the Big Bang to Humankind|last1=Langmuir|first1=C. H.|last2=Broecker|first2=W. S.|year=2012|publisher=Princeton University Press }}</ref>

===The P-P II branch===

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[[File:Nova Centauri 2013 ESO.jpg|thumb|[[Nova Centauri 2013]] is the first in which evidence of lithium has been found.<ref>{{cite web|title=First Detection of Lithium from an Exploding Star|url=http://www.eso.org/public/news/eso1531/|accessdate=29 July 2015|url-status=dead|archiveurl=https://web.archive.org/web/20150801001700/http://www.eso.org/public/news/eso1531/|archivedate=1 August 2015|df=dmy-all}}</ref>]]

Lithium is also found in [[brown dwarf]] substellar objects and certain anomalous orangemetal-poor stars. Because lithium is present in cooler, less massive brown dwarfs, but is destroyed in hotter [[red dwarf]] stars, its presence in the stars' spectra can be used in the "lithium test" to differentiate the two, as both are smaller than the Sun.<ref name=emsley/><ref name="Cain"/><ref>{{cite web|url=http://www-int.stsci.edu/~inr/ldwarf3.html |archive-url=https://archive.today/20130521055905/http://www-int.stsci.edu/~inr/ldwarf3.html |url-status=dead |archive-date=21 May 2013 |title=L Dwarf Classification|accessdate=6 March 2013 | first =N. | last = Reid | date = 10 March 2002}}</ref>

===Less lithium in Sun-like stars with planets===

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===Higher than expected lithium in metal-poor stars===

Certain orangemetal-poor stars can also contain aan abnormally high concentration of lithium.<ref name="high">{{cite journal |doi=10.3847/2041-8213/aaa438|title=Enormous Li Enhancement Preceding Red Giant Phases in Low-mass Stars in the Milky Way Halo|journal=The Astrophysical Journal|volume=852|issue=2|pages=L31|year=2018|last1=Li|first1=H. |last2=Aoki|first2=W. |last3=Matsuno|first3=T. |last4=Kumar|first4=Y. Bharat|last5=Shi|first5=J. |last6=Suda|first6=T. |last7=Zhao|first7=G. |last8=Zhao|first8=G.|bibcode=2018ApJ...852L..31L|arxiv=1801.00090|s2cid=54205417 |doi-access=free }}</ref> Those orangeThese stars foundtended to have a higher than usual concentration of lithium orbit massive objects—neutron stars or black holes—whose gravity evidently pulls heavier lithium to the surface of a hydrogen-helium star, causing more lithium to be observed.<ref name=emsley>{{Cite book|last=Emsley |first=J. |title=Nature's Building Blocks |publisher=Oxford University Press |___location=Oxford|date=2001 |isbn=978-0-19-850341-5}}</ref>

==Proposed solutions==

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Considering the possibility that BBN predictions are sound, the measured value of the primordial lithium abundance should be in error and astrophysical solutions offer revision to it. For example, systematic errors, including ionization correction and inaccurate stellar temperatures determination could affect Li/H ratios in stars. Furthermore, more observations on lithium depletion remain important since present lithium levels might not reflect the initial abundance in the star. In summary, accurate measurements of the primordial lithium abundance is the current focus of progress, and it could be possible that the final answer does not lie in astrophysical solutions.<ref name="fields11" />

Some astronomers suggest that the velocities of nucleons do not follow a [[Maxwell-Boltzmann distribution]]. They test the framework of Tsallis non-extensive statistics. Their result suggest that {{nowrap|1.069 < q < 1.082}} is a possible new solution to the cosmological lithium problem.<ref>{{Cite journal |last1=Hou |first1=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. |title=Non-Extensive Statistics to the Cosmological Lithium Problem |date=2017-01-11 |journal=The Astrophysical Journal |volume=834 |issue=2 |pages=165 |doi=10.3847/1538-4357/834/2/165 |arxiv=1701.04149 |bibcode=2017ApJ...834..165H |s2cid=568182 |issn=1538-4357 |doi-access=free }}</ref>

=== Nuclear physics solutions ===

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Firstly, incorrect or missing reactions could give rise to the lithium problem. For incorrect reactions, major thoughts lie within revision to [[cross section (physics)|cross section]] errors and standard thermonuclear rates according to recent studies.<ref>{{Cite journal|last1=Angulo|first1=C.|last2=Casarejos|first2=E.|last3=Couder|first3=M.|last4=Demaret|first4=P.|last5=Leleux|first5=P.|last6=Vanderbist|first6=F.|last7=Coc|first7=A.|last8=Kiener|first8=J.|last9=Tatischeff|first9=V.|last10=Davinson|first10=T.|last11=Murphy|first11=A. S.|date=September 2005|title=The 7Be(d,p)2α Cross Section at Big Bang Energies and the Primordial 7Li Abundance|journal=Astrophysical Journal Letters|language=en|volume=630|issue=2|pages=L105–L108|doi=10.1086/491732|arxiv=astro-ph/0508454 |bibcode=2005ApJ...630L.105A |issn=0004-637X|doi-access=free}}</ref><ref>{{Cite journal|last1=Boyd|first1=Richard N.|last2=Brune|first2=Carl R.|last3=Fuller|first3=George M.|last4=Smith|first4=Christel J.|date=November 2010|title=New nuclear physics for big bang nucleosynthesis|url=https://ui.adsabs.harvard.edu/abs/2010PhRvD..82j5005B/abstract|journal=Physical Review D |language=en|volume=82|issue=10|pages=105005|doi=10.1103/PhysRevD.82.105005|issn=1550-7998|arxiv=1008.0848|bibcode=2010PhRvD..82j5005B |s2cid=119265813 }}</ref>

Second, starting from [[Fred Hoyle]]'s discovery of a [[Resonance (particle physics)|resonance]] in [[carbon-12]], an important factor in the [[triple-alpha process]], resonance reactions, some of which might have evaded experimental detection or whose effects have been underestimated, become possible solutions to the lithium problem.<ref>{{Cite journal|last1=Hammache|first1=F.|last2=Coc|first2=A.|last3=de Séréville|first3=N.|last4=Stefan|first4=I.|last5=Roussel|first5=P.|last6=Ancelin|first6=S.|last7=Assié|first7=M.|last8=Audouin|first8=L.|last9=Beaumel|first9=D.|last10=Franchoo|first10=S.|last11=Fernandez-Dominguez|first11=B.|date=December 2013|title=Search for new resonant states in 10C and 11C and their impact on the cosmological lithium problem|url=https://ui.adsabs.harvard.edu/abs/2013PhRvC..88f2802H/abstract|journal=Physical Review C|language=en|volume=88|issue=6|pages=062802|doi=10.1103/PhysRevC.88.062802|issn=0556-2813|arxiv=1312.0894|bibcode=2013PhRvC..88f2802H |s2cid=119110688 }}</ref><ref>{{Cite journal|last1=O'Malley|first1=P. D.|last2=Bardayan|first2=D. W.|last3=Adekola|first3=A. S.|last4=Ahn|first4=S.|last5=Chae|first5=K. Y.|last6=Cizewski|first6=J. A.|author6-link= Jolie Cizewski |last7=Graves|first7=S.|last8=Howard|first8=M. E.|last9=Jones|first9=K. L.|last10=Kozub|first10=R. L.|last11=Lindhardt|first11=L.|date=October 2011|title=Search for a resonant enhancement of the 7Be + d reaction and primordial 7Li abundances|url=https://ui.adsabs.harvard.edu/abs/2011PhRvC..84d2801O/abstract|journal=Physical Review C|language=en|volume=84|issue=4|pages=042801|doi=10.1103/PhysRevC.84.042801|bibcode=2011PhRvC..84d2801O |issn=0556-2813}}</ref> These include:

{| border="0"

|- style="height:2em;"

|{{nuclide|link=yes|beryllium|7}}&nbsp;||+&nbsp;||{{nuclide|link=yes|hydrogen|2}}&nbsp;||→&nbsp;||{{nuclide|link=yes|boron|9}}&nbsp;*

|- style="height:2em;"

|{{nuclide|link=yes|beryllium|7}}&nbsp;||+&nbsp;||{{nuclide|link=yes|hydrogen|3}}&nbsp;||→&nbsp;||{{nuclide|link=yes|boron|10}}&nbsp;*

|-

|{{nuclide|link=yes|beryllium|7}}&nbsp;

| +&nbsp;

|{{nuclide|link=yes|helium|3}}&nbsp;

|→&nbsp;

|{{nuclide|link=yes|carbon|10}}&nbsp;*

|}Experimental and theoretical analyses rule out the first and third reactions.<ref name="o946">{{cite journal |last=Cyburt |first=Richard H. |last2=Fields |first2=Brian D. |last3=Olive |first3=Keith A. |last4=Yeh |first4=Tsung-Han |date=2016-02-23 |title=Big bang nucleosynthesis: Present status |url=https://link.aps.org/accepted/10.1103/RevModPhys.88.015004 |journal=Reviews of Modern Physics |volume=88 |issue=1 |page= |doi=10.1103/RevModPhys.88.015004 |issn=0034-6861 |access-date=2025-03-30 |doi-access=free|arxiv=1505.01076 }}</ref>

''[[BBC Science Focus]]'' wrote in 2023 that "recent research seems to completely discount" such theories; the magazine held that mainstream lithium nucleosynthesis calculations are probably correct.<ref name=BBC2023>{{cite news |url=https://www.sciencefocus.com/science/lithium-shortage-universe/ |title=The lithium problem: Why the element keeps disappearing |work=BBC Science Focus Magazine |date=16 June 2023 |author=Alastair Gunn |access-date=17 June 2023}}</ref>

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Dark matter decay and [[supersymmetry]] provide one possibility, in which decaying dark matter scenarios introduce a rich array of novel processes that can alter light elements during and after BBN, and find the well-motivated origin in supersymmetric cosmologies. With the fully operational [[Large Hadron Collider]] (LHC), much of minimal supersymmetry lies within reach, which would revolutionize particle physics and cosmology if discovered;<ref name="fields11" /> however, results from the ATLAS experiment in 2020 have excluded many supersymmetric models.<ref>{{Cite journal|last=Collaboration|first=Atlas|year=2021|title=Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb$^{-1}$ of $\sqrt{s}$ =13 TeV $pp$ collision data with the ATLAS detector|journal=Jhep |volume=02 |page=143 |language=en|doi=10.1007/JHEP02(2021)143|arxiv=2010.14293 |s2cid=256039464 }}</ref><ref>{{Cite web|last=Sutter|first=Paul|date=2021-01-07|title=From squarks to gluinos: It's not looking good for supersymmetry|url=https://www.space.com/no-signs-supersymmetry-large-hadron-collider|access-date=2021-10-29|website=Space.com|language=en}}</ref>

Changing [[fundamental constants]] can be one possible solution, and it implies that first, atomic transitions in metals residing in high-[[redshift]] regions might behave differently from our own. Additionally, Standard Model couplings and particle masses might vary; third, and variation in nuclear physics parameters iswould be needed.<ref name="fields11" />

Nonstandard cosmologies indicate variation of the baryon to photon ratio in different regions. One proposal is a result of large-scale inhomogeneities in cosmic density, different from homogeneity defined in the [[cosmological principle]]. However, this possibility requires a large amount of observations to test it.<ref>{{Cite journal|last1=Holder|first1=Gilbert P.|last2=Nollett|first2=Kenneth M.|last3=van Engelen|first3=Alexander|date=June 2010|title=On Possible Variation in the Cosmological Baryon Fraction|journal=Astrophysical Journal|language=en|volume=716|issue=2|pages=907–913|doi=10.1088/0004-637X/716/2/907|arxiv=0907.3919 |bibcode=2010ApJ...716..907H |issn=0004-637X|doi-access=free}}</ref>

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* [[List of unsolved problems in physics]]

* [[Lithium burning]]

==Further reading==

* {{cite journal |last1=Fields |first1=Brian D. |title=The Primordial Lithium Problem |journal=Annual Review of Nuclear and Particle Science |volume=61 |year=2011 |pages=47–68 |doi=10.1146/annurev-nucl-102010-130445 |arxiv=1203.3551|bibcode=2011ARNPS..61...47F }}

* {{cite journal |doi=10.1103/PhysRevD.83.063006 |title=Resonant destruction as a possible solution to the cosmological lithium problem |date=2011 |last1=Chakraborty |first1=Nachiketa |last2=Fields |first2=Brian D. |last3=Olive |first3=Keith A. |journal=Physical Review D |volume=83 |issue=6 |page=063006 |arxiv=1011.0722 |bibcode=2011PhRvD..83f3006C }}

* {{cite journal |doi=10.1142/S0218301312500048 |title=Resonant Enhancement of Nuclear Reactions as a Possible Solution to the Cosmological Lithium Problem |date=2012 |last1=Cyburt |first1=Richard H. |last2=Pospelov |first2=Maxim |journal=International Journal of Modern Physics E |volume=21 |issue=1 |pages=1250004-1-1250004-13 |arxiv=0906.4373 |bibcode=2012IJMPE..2150004C }}

* {{cite journal |last1=Hou |first1=S. Q. |last2=Yan |first2=H. L. |last3=Li |first3=X. Y. |last4=Zhou |first4=X. H. |last5=Sun |first5=B. |title=Non-Extensive Statistics to the Cosmological Lithium Problem |journal=The Astrophysical Journal |volume=834 |issue=2 |year=2017 |pages=165 |doi=10.3847/1538-4357/834/2/165 |doi-access=free |arxiv=1701.03700|bibcode=2017ApJ...834..165H }}

==References==