The extrapolation properties o/ the relativistic meanrigid model are investigated in nuclear matter. The results of a recent relatlvi~tic Bethe-Brueekner-Goldstone calculation arc taken as 'data'. Fits in a window of normal nuclear densities are e:ttrapolated to large densities and compared with the 'data'. We find large discrepancies which hint at an insufficiency of the model in its present parametrisation.PACS: 21.10.Dr, 21.60.Jz, 21.65.+fThe relativistic mean-field model of nuclei has attracted much attention in the last few years, for reviews see [1][2][3]. It allows ground state properties of finite nuclei to be described with the same high precision (4] as does its nonrelatlvistlc counterpart, the Skyrme-Hartree-Fock model [51. The extrapolative power of the relativistic mean-field model is not yet fully tested. Large scale dynamical calculations are still at an exploratory stage [6}. Linear response features are presently under investigation [7,8], and the equationof-state at high densities is much discussed in high-energy heavy-ion scattering [0] as well as in astrophysical applications [10]. It is the aim of this note to investigate the extrapolation properties of the relativistic mean-field model to high densities in nuclear matter.The relativistic mean-field theory of the nucleus is formulated in terms of a covariant action integral which is understood as an effective action to be used in connection with the mean-field and no-sea approximations. For completeness we give here the ansatz for the Lagrangian density
