  Both the no-core shell model and the effective interaction hyperspherical
harmonic approaches are applied to the calculation of different response
functions to external electromagnetic probes, using the Lorentz integral
transform method. The test is performed on the four-body nuclear system, within
a simple potential model. The quality of the agreement in the various cases is
discussed, together with the perspectives for rigorous ab initio calculations
of cross sections of heavier nuclei.
