Big-Bang reaction rates within the R-matrix model

2005 ◽  
Vol 758 ◽  
pp. 783-786 ◽  
Author(s):  
P. Descouvemont ◽  
A. Adahchour ◽  
C. Angulo ◽  
A. Coc ◽  
E. Vangioni-Flam
Keyword(s):  
Matrix Model ◽  
Reaction Rates ◽  
Big Bang ◽  
R Matrix

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 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 Nuclear physics and its role for describing the early universe

2019 ◽  
Vol 49 ◽  
pp. 1960012 ◽  
Author(s):  
R. G. Pizzone ◽  
R. Spartá ◽  
M. La Cognata ◽  
L. Lamia ◽  
C. Spitaleri ◽  
...  
Keyword(s):  
Cross Sections ◽  
Nuclear Physics ◽  
Reaction Rates ◽  
Big Bang ◽  
Abundance Estimates ◽  
Bare Nucleus ◽  
Trojan Horse Method ◽  
Direct Cross ◽  
Primordial Abundance ◽  
Temperature Ranges

Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of [Formula: see text], [Formula: see text]He and [Formula: see text]He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN [Formula: see text]. These value were then used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances and isotopical composition for H, He and Li. New results on the [Formula: see text]He reaction rate were also taken into account.These were compared with the observational primordial abundance estimates in different astrophysical sites. Reactions to be studied in perspective will also be discussed.

scholarly journals UV regulated star formation in high-redshift galaxies

2019 ◽  
Vol 490 (2) ◽  
pp. 2706-2716 ◽  
Author(s):  
Muhammad A Latif ◽  
Sadegh Khochfar
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Background Radiation ◽  
High Redshift ◽  
Three Dimensional ◽  
Background Level ◽  
Reaction Rates ◽  
Big Bang ◽  
Dense Gas ◽  
First Galaxies

ABSTRACT The first galaxies forming a few hundred million years after the big bang are the key drivers of cosmic evolution and ideal laboratories to study theories of galaxy formation. We here study the role of UV radiation in suppressing star formation in primordial galaxies by destroying molecular hydrogen, the main coolant in primordial gas, and provide estimates of cold dense gas at the onset of star formation. To accomplish this goal, we perform three-dimensional cosmological simulations of minihaloes in different environments forming at z ∼ 25 by varying strength of background UV flux below the Lyman limit between 0.01–1000 in units of $\rm J_{21}=10^{-21}\, erg \,cm^{-2} \,s^{-1} \,Hz^{-1} \,sr^{-1}$. Particularly, we include photodetachment of $\rm H^-$, the self-shielding of $\rm H_2$, which both were neglected in previous studies and use updated reaction rates. Our results show that depending on the background level $\rm H_2$ formation is suppressed, delaying gravitational collapse until haloes reach the atomic cooling limit. We find that the formation of cold dense molecular gas and subsequently star formation gets delayed by 100–230 Myr depending on the level of the background radiation and the growth history of the dark matter haloes. The fraction of dense self-shielded gas is a strong function of the background flux and exponentially declines with the strength of incident UV flux above $\rm J_{21} \ge 1$. We find that taking into account $\rm H_2$ self-shielding is crucial for accurately estimating the amount of cold dense gas available for star formation.

scholarly journals 3He(α,γ)7Be and 3H(α,γ)7Li reaction rates and implication for Big Bang nucleosynthesis in the potential model

2019 ◽  
Vol 49 ◽  
pp. 1960014 ◽  
Author(s):  
S. A. Turakulov ◽  
E. M. Tursunov
Keyword(s):  
Potential Model ◽  
Reaction Rates ◽  
Big Bang ◽  
Abundance Ratio ◽  
Recent Measurement ◽  
Big Bang Nucleosynthesis ◽  
Body Potential ◽  
Text Element ◽  
Good Agreement

The reaction rates of the direct astrophysical capture processes [Formula: see text] and [Formula: see text], as well as the abundance of the [Formula: see text] element are estimated in the framework of a two-body potential model. The estimated [Formula: see text] abundance ratio of [Formula: see text] is in a very good agreement with the recent measurement [Formula: see text] of the LUNA collaboration.

INDIRECT MEASUREMENTS OF NUCLEAR ASTROPHYSICS REACTIONS USING UNSTABLE NUCLEAR BEAMS

2006 ◽  
Vol 15 (08) ◽  
pp. 1899-1907 ◽  
Author(s):  
WEI-PING LIU ◽  
ZHI-HONG LI ◽  
XI-XIANG BAI ◽  
YOU-BAO WANG ◽  
GANG LIAN ◽  
...  
Keyword(s):  
Inverse Kinematics ◽  
Spectroscopic Factor ◽  
Ion Beam ◽  
Nuclear Astrophysics ◽  
Reaction Rates ◽  
Transfer Reactions ◽  
Angular Distributions ◽  
Indirect Measurements ◽  
R Matrix ◽  
Asymptotic Normalization Coefficient

This paper described the nuclear astrophysical studies using the unstable ion beam facility GIRAFFE, by indirect measurements. We measured the angular distributions for some single proton or neutron transfer reactions, such as 7 Be ( d,n )8 B , 11 C ( d,n )12 N , 8 Li ( d,n )9 Be , 8 Li ( d,p )9 Li and 13 N ( d,n )14 O in inverse kinematics, and derived the astrophysical S-factors or reaction rates of 7 Be ( p ,γ)8 B , 11 C ( p ,γ)12 N , 8 Li ( n ,γ)9 Li , 13 N ( p ,γ)14 O by asymptotic normalization coefficient, spectroscopic factor, and R-matrix approach at astrophysically relevant energies.

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