Nuclear matter properties for modified Zimanyi-Moszkowski models

Effective Lagrangians involving nucleons coupled to scalar and vector fields are investigated within the framework of relativistic mean-field theory. The study presents the traditional Walecka model and different kinds of scalar derivative coupling suggested by Zimanyi and Moszkowski (ZM). It is shown that the equations of state for all these modified ZM models are soft. The real part of the optical potential for these models is obtained. When compared with the usual ZM model, the modified models present the peculiarity of giving simultaneously a smaller nucleon effective mass and a smaller incompressibility. This can be explained through the mesonic nonlinear scalar-vector coupling contained in these modified models.