Menezes, D. P.Pinto, M. B.Krein, G. [UNESP]2014-05-272014-05-272000-06-01International Journal of Modern Physics E, v. 9, n. 3, p. 221-247, 2000.0218-3013http://hdl.handle.net/11449/66169We use the optimized linear δ expansion and functional methods to study vacuum contributions in nuclear matter up to the lowest non-trivial order which includes exchange terms. We show that well known results (MFT, RHA and HF) can be easily reproduced when appropriate limits are taken. Neglecting vacuum contributions we explicitly show that the δ expansion goes beyond the traditional loop approximation previously used to study two loop vacuum contributions in nuclear matter. We then evaluate and renormalize vacuum exchange contributions showing that they are numerically very large, as predicted by the ordinary loop approximation.221-247engArtigo10.1142/S0218301300000131WOS:000088668500003Acesso restrito2-s2.0-0034402994