Krein, G. [UNESP]Menezes, D. P.Pinto, M. B.2014-05-272014-05-271996-03-07Physics Letters B. Amsterdam: Elsevier B.V., v. 370, n. 1-2, p. 5-11, 1996.0370-2693http://hdl.handle.net/11449/130454The optimized δ-expansion is used to study vacuum polarization effects in the Walecka model. The optimized δ-expansion is a nonperturbative approach for field theoretic models which combines the techniques of perturbation theory and the variational principle. Vacuum effects on self-energies and the energy density of nuclear matter are studied up to script O sign(δ2). When exchange diagrams are neglected, the traditional relativistic Hartree approximation (RHA) results are exactly reproduced and, using the same set of parameters that saturate nuclear matter in the RHA, a new stable, tightly bound state at high density is found.5-11engNonperturbative field theoryNuclear matterRelativistic nuclear modelsArtigo10.1016/0370-2693(95)01578-7WOS:A1996UA24100002Acesso restrito2-s2.0-0041628970