Effect of nuclear structure on Type Ia supernova nucleosynthesis

Nuclear physics plays an important role in stellar evolution. Fusion, proton capture, and neutron capture are all examples of the importance of the electromagnetic interaction in creating energy that powers stars. Weak interactions in nuclei, including electron capture and β-decay, play an important role in the evolution of both Type Ia and II supernovae and their nucleosynthesis. In this brief article, I will discuss recent progress in understanding the nuclear physics involved in Type Ia explosion mechanisms. I focus on progress made in accurately calculating electron-capture and β-decay rates in iron group nuclei. In order to understand weak processes in nuclei, it becomes necessary to properly describe the nuclear structure of the relevant systems. Short of a complete solution to the many-body problem, the shell model is widely acknowledged to be the appropriate theoretical tool to describe both groundand excited-state properties of nuclei. The shellmodel requires as input a reasonable valence model space and a reliable effective two-body interaction that reproduces known properties of nuclei within the given model space. Such interactions exist for p-, sd-, and pf -shell nuclei, and are under development for heavier or more neutron-rich systems. In this paper, I discuss calculations made in the pf -shell using the two-body effective interaction KB3 [1], or slight modification thereof. The very nature of the quantum many-body problem for fermions – its inherent computational difficulty due to the necessary antisymmetrization of the many-body wavefunction – requires significant computational capability and expertise. This is particularly true of approaches that are trying to treat the many-body problem exactly, or in extremely large shell-model spaces. Standard shell-model diagonalization techniques have recently progressed into the pf -shell [2] while other techniques based on Monte Carlo algorithms have also been quite successful in recent years [3].