Studying medium effects with the optimized $\bdelta$ expansion

Abstract

The possibility of using the optimized $δ$ expansion for studying medium effects on hadronic properties in quark or nuclear matter is investigated. The $δ$ expansion is employed to study density effects with two commonly used models in hadron and nuclear physics, the Nambu--Jona-Lasinio model for the dynamical chiral symmetry breaking and the Walecka model for the equation of state of nuclear matter. The results obtained with the $δ$ expansion are compared to those obtained with the traditional Hartree-Fock approximation. Perspectives for using the $δ$ expansion in other field theoretic models in hadron and nuclear physics are discussed.