Medium effects in electromagnetic form factors

In this paper, the authors explore some of the regions of the nuclear response surface with a relativistic model where the constraints of Poincare invariance and current conservation are specially observed. The use of relativistic interactions implies a strong medium dependence which modifies, in some cases dramatically, the results arrived at by using free form factors. However, as shown for the cases of magnetic moments or transition strengths, these modifications are to a great extent cancelled out by the effects produced by the polarization of the vacuum. The residual medium dependence is, nonetheless, fairly strong thus suggesting the necessity of taking it into account for the calculation of other observables