Speaker
Description
The lightest elements in the universe, such as most helium and some lithium, were forged within the first twenty minutes after the Big Bang through Big Bang Nucleosynthesis (BBN). The theory of BBN features a remarkably small core reaction network of a dozen key nuclear reactions. This theoretical simplicity, combined with precision reaction data from nuclear experiments and cosmological inputs from cosmic microwave background observations, allows BBN to yield high-precision abundance predictions with an accuracy rarely seen in other areas of nuclear astrophysics. By comparing these predictions with precision primordial abundance observations, BBN provides a rigorous test of the standard cosmology and serves as a sensitive probe for new physics beyond the Standard Model in ways complementary to terrestrial experimental search. In this talk, by incorporating the most recent observational inputs, we will firstly report the latest BBN calculations and its constraints on relevant cosmological parameters.
Moving beyond the light elements, neutron captures are crucial processes to create elements heavier than iron on the opposite side of the nuclear chart. The specific neutron density at which neutron capture processes operate in their corresponding astrophysical sites is the primary determinant of their unique nucleosynthesis paths and resulting abundance patterns. The rapid neutron capture process (r-process) occurring in explosive events such as neutron star mergers with extremely abundant free neutron supplies is traditionally held responsible for the enrichment of actinides, in particular Thorium and Uranium. However, recent research suggested a possibility of synthesizing these actinides through the intermediate neutron capture process (i-process) in AGB stars with neutron densities many orders of magnitude lower than those required for the r-process. This possibility could fundamentally change our understanding of galactic chemical evolution. To explore the viability of this alternative scenario, we employed the PRISM code to simulate nucleosynthesis across a range of neutron injection strengths and timescales. We will conclude this talk by comparing specific nucleosynthetic examples where actinides are successfully forged against those where they are once created but depleted by subsequent nuclear reactions, identifying the conditions for i-process actinide survival.
| Keyword-1 | big bang nucleosynthesis |
|---|---|
| Keyword-2 | heavy element nucleosynthesis |
| Keyword-3 | nuclear astrophysics |