These values can be understood in terms of approximate analytic arguments [11,12].
These values can be understood in terms of approximate analytic arguments [11,12].Tags: Principles Of Stellar Evolution And Nucleosynthesis Ebook5 Step Problem SolvingWhen I Have Fears Keats EssayUsc Phd Creative WritingDescriptive Essay About Your Favorite PlaceMock Research PapersIntroduction To A Reflective EssayLiterary Essays Written By
Predictions of the abundances of the light elements, D, 3 He, 4 He, and 7 Li, synthesized at the end of the ‘first three minutes’, are in good overall agreement with the primordial abundances inferred from observational data, thus validating the standard hot Big-Bang cosmology (see [2–4] for reviews).
Big-Bang nucleosynthesis (BBN) offers the deepest reliable probe of the early Universe, being based on well-understood Standard Model physics .
The spread in the curves for D, 3 He, and 7 Li corresponds to the 2σ uncertainties in nuclear cross sections, as estimated by Monte Carlo methods [14,21–23].
The input nuclear data have been carefully reassessed [13, 23–27], leading to improved precision in the abundance predictions.
In particular, the uncertainty in 7 Li/H at interesting values of η has been reduced recently by a factor ∼ 2, a consequence of a similar reduction in the error budget  for the dominant mass-7 production channel 3 He(4 He, γ)7 Be. C38, 090001 (2014) available on the PDG WWW pages (URL: December 4, 2014 4 1. Light Element Abundances BBN theory predicts the universal abundances of D, 3 He, 4 He, and 7 Li, which are essentially fixed by t ∼ 180 s.
Polynomial fits to the predicted abundances and the error correlation matrix have been given [22,29]. 1.1 show the observationally inferred primordial abundances with their associated uncertainties, as discussed below. C38, 090001 (2014) available on the PDG WWW pages (URL: December 4, 2014 1. Abundances are, however, observed at much later epochs, after stellar nucleosynthesis has commenced.
Nearly all neutrons end up bound in the most stable light element 4 He.
Heavier nuclei do not form in any significant quantity both because of the absence of stable nuclei with mass number 5 or 8 (which impedes nucleosynthesis via n4 He, p4 He or 4 He4 He reactions), and the large Coulomb barriers for reactions such as 3 He(4 He, γ)7Li and 3 He(4 He, γ)7 Be.
The nuclear reaction cross sections important for BBN have all been measured at the relevant energies. Big-Bang nucleosynthesis 3 Figure 1.1: The abundances of 4 He, D, 3 He, and 7 Li as predicted by the standard model of Big-Bang nucleosynthesis — the bands show the 95% CL range. This produces heavy elements such as C, N, O, and Fe (‘metals’), while the ejected remains of this stellar processing alters the light element abundances from their primordial values.
We will see, however, that recently there have been substantial advances in the precision of light element observations (e.g., D/H ) and in cosmological parameters (e.g., from Planck). Boxes indicate the observed light element abundances. Thus, one seeks astrophysical sites with low metal abundances, in order to measure light element abundances that are closer to primordial.