Compressibility of nuclear matter and breathing mode of finite nuclei in relativistic random phase approximation

Isoscalar monopole modes in finite nuclei are studied in the framework of relativistic models currently used in ground state calculations. Response functions in the random phase approximation are calculated with nonlinear models for the first time. It is found that some effective Lagrangians having a bulk compression modulus in the range 280-350 MeV can predict correctly breathing mode energies in medium and heavy nuclei. It is pointed out that the parametrization NL1 (K-infinity = 211 MeV) leads to an anomalous behavior of the monopole response.