Solutions of the pion dispersion equation in the medium: new aspects

Abstract

In symmetrical nuclear matter the solutions of pion dispersion equation are investigated in the complex plane of the pion frequency ω. There are three well-known branches of solutions on the physical sheet : sound, pion and isobar, at the matter density less than the critical one ρ<ρ_c. At ρ>ρ_c the fourth branch appears on the physical sheet. For this branch the condition ω^2_c\leq0 (in general case Reω^2_c\leq0) takes place. This points out the instability of the ground state which is possibly related to the pion condensation.

arXiv comment10 pages, Latex, 3 figures; replacement: additional references, talk at Workshop on Quark Condensates in Nuclear Matter, ECT* Trento,Italy,1999