Nucleosynthesis cosmological/primordial

Big efforts have been devoted in the last years to the study of light elements abundances. Definitively their importance is strongly related to cosmology as well as to stellar structure and evolution. In fact hints on the primordial nucleosynthesis can be achieved from Li, Be and B primordial abundances. Moreover these studies can be a precious tool for testing and understanding the inner stellar structure, especially for what regards the mixing processes in stellar envelopes [11-... 

The earliest nucleosynthesis belongs to cosmology. A first flurry of nuclear reactions took place in the great primordial heat occurring between 1 and 100 seconds after the Big Bang. The species H, D, He, He and Li were synthesised in proportions that depend on the baryonic density of the Universe (Vangioni-Flam Cassd 1998) (see Appendix 1). 

Primordial nucleosynthesis really puts the Big Bang cosmology to the test. One might call it a baptism of fire. From these brief but brilliant and fertile beginnings arose a series of light nuclei that are today found everywhere in nature above all hydrogen, followed by helium, which between them amount to 98% of the total mass of atomic matter in the Universe. 

The paper is organized as follows in section 2, we briefly review the geometry and dynamics of the Universe and then give the Einstein-Friedman-Lemaitre (hereafter EEL) equations section 3 introduces some important quantities needed for observations in section 4, we rapidly present some solutions of the EEL equations, i.e. some cosmological models in section 5, the Standard Big Bang Nucleosynthesis Model is described while section 6 shows a statement of observations of primordial abundances in section 7, we confront the predictions of the Standard Big Bang Nucleosynthesis (hereafter SBBN) model to the observations of the primordial abundances a brief conclusion is... 

Cosmological nucleosynthesis studies predict that the conditions characterizing the Big Bang are consistent with the synthesis only of the lightest elements H, H, He, " He, and Li (Buries et al., 2001 Cyburt et al., 2002). These contributions define the primordial compositions both of galaxies and of the first stars formed therein. 

One of the major achievements in cosmology is that it can account simultaneously for the primordial abundances of H, D, 3He, 4IIc and 7Li but only for a low density universe. The comparison between the observed primordial abundances and the Big Bang nucleosynthesis calculations can allow to impose constraints upon the baryon to photon ratio (rj) in the universe. In particular, for a baryon to photon ratio r/ 3 10 10 the baryonic density parameter of the universe is (Peacock, 1999) ... 

The distribution of elements in the cosmos is the result of many different physical processes in the history of the Universe, from Big Bang to present times. Its study provides us with a powerful tool for understanding the physical conditions of the primordial cosmos, the physics of nucleosynthesis processes that occur in different objects and places, and the formation and evolution of stars and galaxies. Cosmochemistry is a fundamental topic for many different branches of Astrophysics as Cosmology, Stellar Structure and Evolution, Interstellar Medium, and Galaxy Formation and Evolution. 

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