Tachyon Pole in σ Meson Propagator in Nuclear Matter in the Relativistic σ-ω Model

The conditions that the tachyon pole of the σ meson propagator in nuclear matter appears are studied in the one-loop approximation in the relativistic σ-ω model. Different from the results of the previous paper, we find that the effect of the constant a in the self-interaction, U(σ) = aσ + 1/21bσ2 + 1/31cσ3 + 1/41dσ4, of the σ meson cannot be neglected. It determines the critical density where tachyon appears. The smaller the a, the larger the critical density. The binding energy, pressure, incompressibility coefficient, nucleon effective mass are calculated and the relation between parameters to the tachyon pole is also studied.