Nuclear fusion data of light-mass nuclei are particularly important for studying the origin of atomic nuclides in the Universe.

Massive stars culminate their evolution by supernova (SN) explosion which is presumed to be most viable astrophysical site of r-process nucleosynthesis. Even in the nucleosynthesis of heavy elements, initial entropy and density in the neutrino-driven wind of Type II SNe are so high that nuclear statistical equilibrium favors production of abundant light nuclei. In such explosi ve circumstances many nuclear processes similar to the Big-Bang nucleosynthesis operate in the production of the alpha-process and r-process nucleosyntheses. Light-mass nuclei which include neutron-rich radioactive nuclei as well as heavy-mass nuclei pla y the significant roles in the r-process [1,2]. In this paper we discuss supernova nucleosynthesis in order to identify that Type II SNe could be a successful site for r-process nucleosynthesis [3]. We also discuss cosmochronometry to use long lived r-p rocess nuclei like ²³²Th (half life = 14.05 Gy) and ²³⁸U (4.47 Gy) in order to constrain the still unresolved potential difficulty of the cosmic age problem [4,5].

The Big-Bang nucleosynthesis (BBN) is another site of explosive nucl eosynthesis. Rrecent data of cosmic microwave background (CMB) anisotropy have suggested that the Universe is occupied by 27% unknown dark matter and 69% mysterious dark energy with a tiny fraction of 4% baryonic matter. It is one of the biggest and challenging problems in modern physics and astronomy to find the true nature of dark matter [6] and dark energy[7]. This 4% baryonic fraction is at least 1-2σ above the optimum value determined from the standard BBN model. Baryon inhomogeneous BBN (IBBN) [8,9] with neutrino lepton-number [10] symmetry was proposed in order to resolve this discrepancy . Although baryonic fraction is tiny in total universal mass density, BBN plays the critical roles in strongly constraining the theoretical models of dark energy and dark matter. We will discuss how the nuclear fusion data in the BBN plays a critical role in the studies of cosmological theories..

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