scholarly journals Big-Bang nucleosynthesis: Constraints on nuclear reaction rates, neutrino degeneracy, inhomogeneous and Brans–Dicke models

2017 ◽  
Vol 26 (08) ◽  
pp. 1741003 ◽  
Author(s):  
Riou Nakamura ◽  
Masa-Aki Hashimoto ◽  
Ryotaro Ichimasa ◽  
Kenzo Arai
Keyword(s):  
Cosmological Constant ◽  
Nuclear Reaction ◽  
Recent Progress ◽  
Reaction Rates ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Friedmann Model ◽  
Theory Of Gravitation ◽  
The Big Bang

We review the recent progress in the Big-Bang nucleosynthesis which includes the standard and nonstandard theory of cosmology, effects of neutrino degeneracy, and inhomogeneous nucleosynthesis within the framework of a Friedmann model. As for a nonstandard theory of gravitation, we adopt a Brans–Dicke theory which incorporates a cosmological constant. We constrain various parameters associated with each subject.

scholarly journals Underground Nuclear Astrophysics: Present and future of the LUNA experiment

2019 ◽  
Vol 209 ◽  
pp. 01043
Author(s):  
Carlo Gustavino
Keyword(s):  
Nuclear Astrophysics ◽  
Reaction Rates ◽  
Big Bang ◽  
Scientific Program ◽  
Thermonuclear Reaction ◽  
Big Bang Nucleosynthesis ◽  
Celestial Bodies ◽  
Deep Underground ◽  
The Big Bang ◽  
Nuclear Processes

The evolution of celestial bodies is regulated by gravitation and thermonuclear reaction rates, while the Big Bang nucleosynthesis is the result of nuclear processes in a rapidly expanding Universe. The LUNA Collaboration has shown that, by exploiting the ultra low background achievable deep underground, it is possible to study the relevant nuclear processes down to the nucleosynthesis energy inside stars and during the first minutes of Universe. In this paper the main results of LUNA are overviewed, as well as the scientific program the forthcoming 3.5 MV underground accelerator.

scholarly journals Bayesian Estimation of the D(p,γ)3He Thermonuclear Reaction Rate

2021 ◽  
Vol 923 (1) ◽  
pp. 49
Author(s):  
Joseph Moscoso ◽  
Rafael S. de Souza ◽  
Alain Coc ◽  
Christian Iliadis
Keyword(s):  
Reaction Rates ◽  
Big Bang ◽  
Baryon Density ◽  
Thermonuclear Reaction ◽  
Big Bang Nucleosynthesis ◽  
Highly Sensitive ◽  
Theoretical Predictions ◽  
Reliable Knowledge ◽  
Percent Accuracy ◽  
The Big Bang

Abstract Big bang nucleosynthesis (BBN) is the standard model theory for the production of light nuclides during the early stages of the universe, taking place about 20 minutes after the big bang. Deuterium production, in particular, is highly sensitive to the primordial baryon density and the number of neutrino species, and its abundance serves as a sensitive test for the conditions in the early universe. The comparison of observed deuterium abundances with predicted ones requires reliable knowledge of the relevant thermonuclear reaction rates and their corresponding uncertainties. Recent observations reported the primordial deuterium abundance with percent accuracy, but some theoretical predictions based on BBN are in tension with the measured values because of uncertainties in the cross section of the deuterium-burning reactions. In this work, we analyze the S-factor of the D(p,γ)3He reaction using a hierarchical Bayesian model. We take into account the results of 11 experiments, spanning the period of 1955–2021, more than any other study. We also present results for two different fitting functions, a two-parameter function based on microscopic nuclear theory and a four-parameter polynomial. Our recommended reaction rates have a 2.2% uncertainty at 0.8 GK, which is the temperature most important for deuterium BBN. Differences between our rates and previous results are discussed.

scholarly journals Revised uncertainties in Big Bang Nucleosynthesis

2017 ◽  
Vol 26 (08) ◽  
pp. 1741008 ◽  
Author(s):  
M. Foley ◽  
N. Sasankan ◽  
M. Kusakabe ◽  
G. J. Mathews
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Analysis ◽  
Reaction Rates ◽  
Big Bang ◽  
Effective Number ◽  
Big Bang Nucleosynthesis ◽  
The Big Bang

Big Bang Nucleosynthesis (BBN) explores the first few minutes of nuclei formation during the Big Bang. We present updated 2[Formula: see text] for the abundances of the four primary light nuclides — D, 3He, 4He, and 7Li — in BBN. A modified standard BBN code was used in a Monte Carlo analysis of the nucleosynthesis uncertainties as a function of the baryon-to-photon ratio. Reaction rates were updated to those of NACRE, REACLIB, and [Formula: see text]-Matrix calculations. The results were then used to derive a new constraint on the effective number of neutrinos.

scholarly journals Effects of transient nonthermal particles on the big bang nucleosynthesis

2020 ◽  
Vol 29 (03) ◽  
pp. 2050012
Author(s):  
Tae-Sun Park ◽  
Kyung Joo Min ◽  
Seung-Woo Hong
Keyword(s):  
Reaction Rates ◽  
Big Bang ◽  
Temporal Region ◽  
Temporal Position ◽  
Strongly Correlated ◽  
Light Elements ◽  
Big Bang Nucleosynthesis ◽  
Wide Range ◽  
The Big Bang ◽  
Nonthermal Particles

The effects of introducing a small amount of nonthermal distribution (NTD) of elements in big bang nucleosynthesis (BBN) are studied by allowing a fraction of the NTD to be time-dependent so that it contributes only during a certain period of the BBN evolution. The fraction is modeled as a Gaussian-shaped function of [Formula: see text], where [Formula: see text] is the temperature of the cosmos, and thus the function is specified by three parameters; the central temporal position, the width and the magnitude. The change in the average nuclear reaction rates due to the presence of the NTD is assumed to be proportional to the Maxwellian reaction rates but with temperature [Formula: see text], [Formula: see text] being another parameter of our model. By scanning a wide four-dimensional parametric space at about half a million points, we have found about 130 points with [Formula: see text], at which the predicted primordial abundances of light elements are consistent with the observations. The magnitude parameter [Formula: see text] of these points turns out to be scattered over a very wide range from [Formula: see text] to [Formula: see text], and the [Formula: see text]-parameter is found to be strongly correlated with the magnitude parameter [Formula: see text]. The temperature region with [Formula: see text] or the temporal region [Formula: see text][Formula: see text]s seems to play a central role in lowering [Formula: see text].

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 Compilation and R-matrix analysis of Big Bang nuclear reaction rates

2004 ◽  
Vol 88 (1) ◽  
pp. 203-236 ◽  
Author(s):  
Pierre Descouvemont ◽  
Abderrahim Adahchour ◽  
Carmen Angulo ◽  
Alain Coc ◽  
Elisabeth Vangioni-Flam
Keyword(s):  
Nuclear Reaction ◽  
Reaction Rates ◽  
Big Bang ◽  
Matrix Analysis ◽  
R Matrix

scholarly journals Nonlinear matter terms in general scalar–tensor braneworld cosmology

2019 ◽  
Vol 28 (11) ◽  
pp. 1950138
Author(s):  
Kevin F. S. Pardede ◽  
Agus Suroso ◽  
Freddy P. Zen
Keyword(s):  
Big Bang ◽  
Accelerated Expansion ◽  
Big Bang Nucleosynthesis ◽  
Braneworld Cosmology ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
General Scalar ◽  
Bulk Scalar Field ◽  
The Big Bang ◽  
Correction Terms

A five-dimensional braneworld cosmological model in general scalar–tensor action that is comprised of various Horndeski Lagrangians is considered. The Friedmann equations in the case of strongly and weakly coupled [Formula: see text] Horndeski Lagrangians have been obtained. The strongly coupled [Formula: see text] model produces the Cardassian term [Formula: see text] with [Formula: see text], which can serve as an alternative explanation for the accelerated expansion phase of the universe. Furthermore, the latest combined observational facts from BAO, CMB, SNIa, [Formula: see text] and [Formula: see text] value observation suggest that the [Formula: see text] term lies quite close to the constrained value. On the other hand, the weakly coupled [Formula: see text] case has several new correction terms which are omitted in the braneworld Einstein–Hilbert model, e.g. the cubic [Formula: see text] and the dark radiation–matter interaction term [Formula: see text]. Furthermore, this model provides a cosmological constant constructed from the bulk scalar field, requires no brane tension and supports the big bang nucleosynthesis (BBN) constraint naturally.

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