Microscopic description of nuclear reactions starting from the ab initio no-core shell model

One of the greatest challenges for nuclear physics today is the development of a quantitative, microscopic theory of low-energy reactions on light nuclei. We have explored two avenues for the microscopic calculations of nuclear-reaction properties starting from the nuclear structure of the ab initio no-core shell model (NCSM): i) the Lorentz integral transform (LIT) approach, and ii) the resonating-group method (RGM). During this presentation I will highlight a recent application of the NCSM/LIT approach to the ab initio calculation of the 4He total photo-absorption cross section using two- plus three-nucleon interactions based upon chiral effective-field theory. In the second part of the talk, I will outline the NCSM/RGM approach and present its application to neutron-4He scattering.