scholarly journals Neutrinos and Big Bang Nucleosynthesis

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Gary Steigman
Keyword(s):  
Particle Physics ◽  
Weak Interactions ◽  
Big Bang ◽  
Baryon Density ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry ◽  
Lithium Abundance ◽  
Dark Radiation ◽  
Cosmic Neutrino Background ◽  
Neutrino Background

According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders this neutrino background undetectable with current technology. The cosmic neutrino background can, however, be probed indirectly through its cosmological effects on big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) radiation. In this BBN review, focused on neutrinos and more generally on dark radiation, the BBN constraints on the number of “equivalent neutrinos” (dark radiation), on the baryon asymmetry (baryon density), and on a possible lepton asymmetry (neutrino degeneracy) are reviewed and updated. The BBN constraints on dark radiation and on the baryon density following from considerations of the primordial abundances of deuterium and helium-4 are in excellent agreement with the complementary results from the CMB, providing a suggestive, but currently inconclusive, hint of the presence of dark radiation, and they constrain any lepton asymmetry. For all the cases considered here there is a “lithium problem”: the BBN-predicted lithium abundance exceeds the observationally inferred primordial value by a factor of~3.

scholarly journals Li isotopes in metal-poor halo dwarfs: a more and more complicated story

2009 ◽  
Vol 5 (S268) ◽  
pp. 201-210
Author(s):  
Monique Spite ◽  
François Spite
Keyword(s):  
Cosmic Rays ◽  
Big Bang ◽  
The Other ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
The Galaxy ◽  
Li Isotope ◽  
Low Metallicity ◽  
The Big Bang ◽  
Early Galaxy

AbstractThe nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis.The 7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the ν process). 6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a “plateau” of the abundance of 7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H] < −2.7dex) the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (logϵ(Li) = A(7Li) = 2.2 dex) is much lower than the the value (logϵ(Li) = 2.72) predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of 7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked.A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the 6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of 6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing 6Li?

scholarly journals Lepton asymmetry, neutrino spectral distortions, and big bang nucleosynthesis

2017 ◽  
Vol 95 (6) ◽  
Author(s):  
E. Grohs ◽  
George M. Fuller ◽  
C. T. Kishimoto ◽  
Mark W. Paris
Keyword(s):  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry

scholarly journals A Scale at 10 MeV, Gravitational Topological Vacuum, and Large Extra Dimensions

Universe ◽  
2018 ◽  
Vol 4 (7) ◽  
pp. 80
Author(s):  
Ufuk Aydemir
Keyword(s):  
Thermal History ◽  
Extra Dimensions ◽  
Weak Interactions ◽  
Large Extra Dimensions ◽  
Big Bang ◽  
Length Scale ◽  
Big Bang Nucleosynthesis ◽  
History Of ◽  
The Universe ◽  
Bonnet Term

We discuss a possible scale of gravitational origin at around 10 MeV, or 10−12 cm, which arises in the MacDowell–Mansouri formalism of gravity due to the topological Gauss–Bonnet term in the action, as pointed out by Bjorken several years ago. A length scale of the same size emerges also in the Kodama solution in gravity, which is known to be closely related to the MacDowell–Mansouri formulation. We particularly draw attention to the intriguing incident that the existence of six compact extra dimensions originated from TeV-scale quantum gravity as well points to a length scale of 10−12 cm, as the compactification scale. The presence of six such extra dimensions is also in remarkable consistency with the MacDowell–Mansouri formalism; it provides a possible explanation for the factor of ∼10120 multiplying the Gauss–Bonnet term in the action. We also comment on the relevant implications of such a scale regarding the thermal history of the universe motivated by the fact that it is considerably close to 1–2 MeV below which the weak interactions freeze out, leading to Big Bang Nucleosynthesis.

scholarly journals Can one measure the Cosmic Neutrino Background?

2017 ◽  
Vol 26 (01n02) ◽  
pp. 1740008 ◽  
Author(s):  
Amand Faessler ◽  
Rastislav Hodák ◽  
Sergey Kovalenko ◽  
Fedor Šimkovic
Keyword(s):  
Rest Mass ◽  
Big Bang ◽  
Electron Neutrino ◽  
Electron Neutrinos ◽  
Cosmic Neutrino Background ◽  
Cosmic Neutrino ◽  
The Moment ◽  
Katrin Experiment ◽  
The Big Bang ◽  
Neutrino Background

The Cosmic Microwave Background (CMB) yields information about our Universe at around 380,000 years after the Big Bang (BB). Due to the weak interaction of the neutrinos with matter, the Cosmic Neutrino Background (CNB) should give information about a much earlier time of our Universe, around one second after the BB. Probably, the most promising method to “see” the CNB is the capture of the electron neutrinos from the Background by Tritium, which then decays into 3He and an electron with the energy of the the [Formula: see text]-value [Formula: see text] 18.562[Formula: see text]keV plus the electron neutrino rest mass. The “KArlsruhe TRItium Neutrino” (KATRIN) experiment, which is in preparation, seems presently the most sensitive proposed method for measuring the electron antineutrino mass. At the same time, KATRIN can also look by the reaction [Formula: see text]. The capture of the Cosmic Background Neutrinos (CNB) should show in the electron spectrum as a peak by the electron neutrino rest mass above [Formula: see text]. Here, the possibility to see the CNB with KATRIN is studied. A detection of the CNB by KATRIN seems not to be possible at the moment. But KATRIN should be able to determine an upper limit for the local electron neutrino density of the CNB.

scholarly journals THE 2H(α, γ)6LI REACTION AT LUNA AND BIG BANG NUCLEOSYNTHETIS

2013 ◽  
Vol 53 (A) ◽  
pp. 534-537 ◽  
Author(s):  
Carlo Gustavino
Keyword(s):  
Cross Section ◽  
Preliminary Data ◽  
Big Bang ◽  
Low Energy ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
Halo Stars ◽  
First Time ◽  
Standard Production ◽  
Production Channel

The <sup>2</sup>H(α, γ)<sup>6</sup>Li reaction is the leading process for the production of <sup>6</sup>Li in standard Big Bang Nucleosynthesis. Recent observations of lithium abundance in metal-poor halo stars suggest that there might be a 6Li plateau, similar to the well-known Spite plateau of <sup>7</sup>Li. This calls for a re-investigation of the standard production channel for <sup>6</sup>Li. As the <sup>2</sup>H(α, γ)<sup>6</sup>Li cross section drops steeply at low energy, it has never before been studied directly at Big Bang energies. For the first time the reaction has been studied directly at Big Bang energies at the LUNA accelerator. The preliminary data and their implications for Big Bang nucleosynthesis and the purported <sup>6</sup>Li problem will be shown.

scholarly journals Big-Bang Nucleosynthesis and Primordial Lithium Abundance Problem

2019 ◽  
Vol 128 (5) ◽  
pp. 707-712 ◽  
Author(s):  
V. Singh ◽  
J. Lahiri ◽  
D. Bhowmick ◽  
D. N. Basu
Keyword(s):  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance

scholarly journals Lithium pollution of a white dwarf records the accretion of an extrasolar planetesimal

Science ◽  
2020 ◽  
Vol 371 (6525) ◽  
pp. 168-172
Author(s):  
B. C. Kaiser ◽  
J. C. Clemens ◽  
S. Blouin ◽  
P. Dufour ◽  
R. J. Hegedus ◽  
...  
Keyword(s):  
Solar System ◽  
White Dwarf ◽  
Big Bang ◽  
Early Solar System ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
Sodium Potassium ◽  
Elemental Abundances ◽  
Exoplanetary Systems ◽  
Gaia Dr2

Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the composition of the nebula from which the systems formed, which is analogous to how meteorite abundances inform our understanding of the early Solar System. We report the detection of lithium, sodium, potassium, and calcium in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to the accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and, with the exception of lithium, they are consistent with meteoritic values in the Solar System. We compare the measured lithium abundance with measurements in old stars and with expectations from Big Bang nucleosynthesis.

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