Big-Bang Nucleosynthesis and Primordial Lithium Abundance Problem

Singh, Vinay; Lahiri, Joydev; Bhowmick, Debasis; Basu, Debabrata

doi:10.1134/s1063776119040058

Cited by 8 publications

(3 citation statements)

References 37 publications

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“…It is well known that during the first few minutes of the universe lifetime, nuclear reactions took place and produced light elements such as 4 He, D, 3 He and 7 Li. Using standard calculations one can estimate the abundance of these elements and find good agreement with the observations up to the baryon-to-photon ratio, η, which is extracted from CMB measurements [7,8]. Moreover, by fix-ing η, no free parameter is left in the Big Bang Nucleosynthesis (BBN) calculations and the primordial abundances of these elements are thus affected only by tamed uncertainties in the nuclear cross-section [9].…”

mentioning

confidence: 83%

Light Dark Matter: A Common Solution to the Lithium and ${H_0}$ Problems

Alcaniz,

Bernal,

Masiero

et al. 2019

Preprint

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Currently, the standard cosmological model faces some tensions and discrepancies between observations at early and late cosmological time. One of them concerns the well-known H0-tension problem, i.e., a ∼ 4.4σdifference between the early-time estimate and late-time measurements of the Hubble constant, H0. Another puzzling question rests in the cosmological lithium abundance, where again local measurements differ from the one predicted by Big Bang Nucleosynthesis (BBN). In this work, we show that a mechanism of light dark matter production might hold the answer for these questions. If dark matter particles are sufficiently light and a fraction of them were produced non-thermally in association with photons, this mechanism has precisely what is needed to destroy Lithium without spoiling other BBN predictions. Besides, it produces enough radiation that leads to a larger H0 value, reconciling early and late-time measurements of the Hubble expansion rate without leaving sizable spectral distortions in the Cosmic Microwave Background spectrum.

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mentioning

confidence: 83%

Light Dark Matter: A Common Solution to the Lithium and ${H_0}$ Problems

Alcaniz,

Bernal,

Masiero

et al. 2019

Preprint

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“…6 Li is the most problematic among all the light elements. 7,11 The lower bound on 7 Li abundance is deduced from old metal poor stars in the Galactic halo where the lithium abundance is almost independent of metallicity, forming the so-called spite plateau. This plateau is interpreted as the BBn yield, assuming that lithium has not been depleted at the surface of the stars.…”

Section: Primordial Nucleosynthesismentioning

confidence: 99%

Prebiotic Chemistry and Life's Origin

2022

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According to our current understanding, the Universe starts roughly 13.7 billion years ago. The earliest phases of the Big Bang are subject to much speculation since astronomical data about them are not available. In the most common models, the Universe was filled homogeneously and isotropically with a very high energy density and huge temperatures and pressures, and was very rapidly expanding and cooling.In the first 10 −43 seconds of its existence, called the Planck epoch, the Universe was very compact. It's thought that at such a dense energetic state, the four fundamental forces -gravity, electromagnetism and the strong and weak nuclear forces -were forged into a single force. The Planck epoch was succeeded by the grand unification epoch, during which gravitation separated from the other forces as the Universe's temperature fell. At about 10 −37

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“…In fact it is not surprising that attempts at resolving the Li Problem by re-examination of the standard BBN rates failed [73,110,111] as these are the same rates operating in the Sun and confirmed by solar neutrino flux observations. Other rates such as 7 Be(n, p) 7 Li [112, 113], 7 Be(n, α) 4 He [114][115][116][117], 7 Be(d, pα) 4 He [118], 7 Be(α, γ) 11 C [119], 7 Li(d, nα) 4 He [120] have been recently been (re)measured (or re-evaluated [121]), though none of these rates make more than a marginal change in the final 7 Li abundance.…”

Section: The Primordial 7 LI Problemmentioning

confidence: 99%

Implications of the non-observation of ⁶Li in halo stars for the primordial ⁷Li problem

Fields

Olive

2022

J. Cosmol. Astropart. Phys.

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The primordial Lithium Problem is intimately connected to the assumption that the 7Li abundance observed in metal-poor halo stars is unchanged from its primordial value, which lies significantly below the predictions of standard big-bang nucleosynthesis. Two key lines of evidence have argued that these stars have not significantly depleted their initial (mostly primordial) 7Li: i) the lack of dispersion in Li abundance measurements at low metallicity (and high surface temperature); and ii) the detection of the more fragile 6Li isotope in at least two halo stars. The purported 6Li detections were in good agreement with predictions from cosmic-ray nucleosynthesis which is responsible for the origin of 6Li. This concordance left little room for 6Li depletion, and the apparent 6Li survival implied that 7Li largely evaded destruction, because stellar interiors destroy 6Li more vigorously then than 7Li. Recent (re)-observations of halo stars challenge the evidence against 7Li depletion: i) lithium elemental abundances now show significant dispersion, and ii) sensitive 6Li searches now reveal only upper limits to the 6Li/7Li ratio. We discuss the consequences of these 6Li non-detections on the primordial 7Li Problem, Galactic cosmic-ray nucleosynthesis, and the question of differential depletion of Li in stars. The tight new 6Li upper limits generally fall far below the predictions of cosmic-ray nucleosynthesis, implying that substantial 6Li depletion has occurred — by factors up to 50. We show that in stars with 6Li limits and thus lower bounds on 6Li depletion, an equal amount of 7Li depletion is more than sufficient to resolve the primordial 7Li Problem. This picture is consistent with well-studied stellar models in which 7Li is less depleted than 6Li, and strengthen the case that the Lithium Problem has an astrophysical solution. We conclude by suggesting future observations that could test these ideas.

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Big-Bang Nucleosynthesis and Primordial Lithium Abundance Problem

Cited by 8 publications

References 37 publications

Light Dark Matter: A Common Solution to the Lithium and ${H_0}$ Problems

Light Dark Matter: A Common Solution to the Lithium and ${H_0}$ Problems

Prebiotic Chemistry and Life's Origin

Implications of the non-observation of ⁶Li in halo stars for the primordial ⁷Li problem

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Big-Bang Nucleosynthesis and Primordial Lithium Abundance Problem

Cited by 8 publications

References 37 publications

Light Dark Matter: A Common Solution to the Lithium and ${H_0}$ Problems

Light Dark Matter: A Common Solution to the Lithium and ${H_0}$ Problems

Prebiotic Chemistry and Life's Origin

Implications of the non-observation of 6Li in halo stars for the primordial 7Li problem

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Implications of the non-observation of ⁶Li in halo stars for the primordial ⁷Li problem