Instabilities of relativistic mean field models and the role of nonlinear terms

The instability of nuclear matter due to particle-hole excitation modes has been studied in the frame-work of several relativistic mean field (RMF) models. It is found that both the longitudinal and the transversal modes depend sensitively on the parameter sets used. The important impact of the vector and vector-scalar nonlinear terms on the stability of both modes is demonstrated. Our finding corroborates the result of previous studies, namely that certain RMF models cannot be used in high density applications. However, we show that for certain parameter sets of RMF models this shortcoming can be alleviated by adding these nonlinear terms.