The mean pi-field should be calculated in a relativistic mean field theoryfor nuclear matter

We extend our work on the finite value of mean rr-field in the relativistic mean field theory to the derivative coupling models for nuclear matter pro posed by Zimanyi and Moszkowski. We show that a finite mean pi-field may lo wer the energy per nucleon at a not too high density for all of those model s. This qualitative result seems true in general and is model independent, although the quantitative details may be different for different models.