  We review different models used for reactions involved in nuclear
astrophysics. The reaction rate is defined for resonant as well as for
non-resonant processes. For low-density nuclei, we describe the DWBA method,
the potential model, the R-matrix method, and microscopic cluster models. The
statistical model is developed for high-level densities. Details of
calculations in the low- and high-density regimes are illustrated with new
results concerning transfer reactions and level densities.

Astrophysics;Nuclear Theory