What is the big-bang-nucleosynthesis prediction for the baryon density and how reliable is it?

2001 ◽  
Vol 63 (6) ◽  
Author(s):  
Scott Burles ◽  
Kenneth M. Nollett ◽  
Michael S. Turner
Keyword(s):  
Big Bang ◽  
Baryon Density ◽  
Big Bang Nucleosynthesis ◽  
The Big Bang

scholarly journals A BGO set-up for the direct measurement of the D(p,γ)3He fusion cross section at LUNA

2020 ◽  
Vol 1668 (1) ◽  
pp. 012028
Author(s):  
Viviana Mossa
Keyword(s):  
Cross Section ◽  
Cosmic Time ◽  
Fusion Cross Section ◽  
Big Bang ◽  
Baryon Density ◽  
Reaction Cross ◽  
Big Bang Nucleosynthesis ◽  
Primordial Abundance ◽  
Set Up ◽  
The Big Bang

Abstract The Big Bang Nucleosynthesis (BBN) describes the production of light nuclides occurred during the first minutes of cosmic time. It started with the accumulation of deuterium, whose primordial abundance is sensitive to the universal baryon density and to the amount of relativistic particles. Currently the main source of uncertainty to an accurate theoretical deuterium abundance evaluation is due to the poor knowledge of the D(p, γ)3He cross section at BBN energies. The present work wants to describe one of the two experimental approaches proposed by the LUNA collaboration, whose goal is to measure with unprecedented precision, the reaction cross section in the energy range 30 < Ecm[keV] < 300.

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 Big Bang Nucleosynthesis

2002 ◽  
Vol 187 ◽  
pp. 1-15
Author(s):  
D.N. Schramm
Keyword(s):  
Systematic Error ◽  
Big Bang ◽  
Baryon Density ◽  
Galactic Evolution ◽  
Big Bang Nucleosynthesis ◽  
X Ray ◽  
Baryonic Density ◽  
The Big Bang ◽  
The Universe

Big Bang Nucleosynthesis (BBN) is on the verge of undergoing a transformation now that extragalactic deuterium is being measured. Previously, the emphasis was on demonstrating the concordance of the Big Bang Nucleosynthesis model with the abundances of the light isotopes extrapolated back to their primordial values using stellar and Galactic evolution theories. Once the primordial deuterium abundance is converged upon, the nature of the field will shift to using the much more precise primordial D/H to constrain the more flexible stellar and Galactic evolution models (although the question of potential systematic error in 4He abundance determinations remains open). The remarkable success of the theory to date in establishing the concordance has led to the very robust conclusion of BBN regarding the baryon density. The BBN constraints on the cosmological baryon density are reviewed and demonstrate that the bulk of the baryons are dark and also that the bulk of the matter in the universe is non-baryonic. Comparison of baryonic density arguments from Lyman-α clouds, x-ray gas in clusters, the Sunyaev-Zeldovich effect, and the microwave anisotropy are made and shown to be consistent with the BBN value.

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 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.

Deuterium in the Galaxy

1977 ◽  
Vol 3 (2) ◽  
pp. 100-101 ◽  
Author(s):  
R. D. Brown
Keyword(s):  
Great Majority ◽  
Big Bang ◽  
Baryon Density ◽  
The Galaxy ◽  
Mass Fractions ◽  
Expansion Of The Universe ◽  
Sensitive Function ◽  
The Big Bang ◽  
Deuterium Production ◽  
The Universe

There have been a number of attempts made in the last decade or two to observe deuterium in parts of the universe other than here in Earth. It is of interest merely to detect deuterium elsewhere just as it is to detect the occurrence of any nuclide. However in the case of deuterium there is a special interest because in big-bang cosmologies the great majority of deuterium in the universe is considered to have been formed in the initial fireball (Wagoner, 1973). Any observation of the present abundance of deuterium thus might give information about the very early stages of the creation of the universe. Detailed studies of nucleosynthesis during the early expansion of hot big-bang universes have however indicated a particular feature of deuterium production. (Fig. 1) The mass fraction produced X(D) is a very sensitive function of the size of the universe, as measured say by the present baryon density ϱb. Other nuclides that are mainly produced in the early expansion, such as 4He, have mass fractions less dependent on ϱb. Thus if we adopt the big-bang model for our universe we can determine ϱb from observations of X(D). Apart from any intrinsic interest in the present density of the’universe, there is considerable interest in whether the value is great enough for the present expansion to halt and go over to a collapse — or so small that the expansion of the universe will go on forever.

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.

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