Nuclear structure, nuclear force and spin-isospin excitations in stellar processes

The spin-isospin Nucleon-Nucleon (\textit{NN}) force plays crucial roles in determining shell structure of exotic nuclei. Even magic numbers can be destroyed. We will overview what changes can be expected in exotic nuclei on single-particle properties and spin-isospin excitations, including Gamov-Teller processes. The Gamov-Teller and other weak processes can be well studied by recent shell model calculations with newly determined effective \textit{NN} interactions. We shall survey such new results, and look at possible implications on stellar processes. The calculations include full pf-shell calculations and pf+g$_{9/2}$ calculations. We may discuss the stability of $^{78}$Ni core in exotic Ni isotopes and its implications in the r-process. Within the pf-shell, the Gamov-Teller properties will be assessed in view of their influences on stellar processes. Such studies will provide us with some information on neutrino reactions.