The Gamow-Teller states and sum rule in relativistic models

The giant Gamow-Teller (GT) states and the CT sum rule are investigated in relativistic models. It is shown that the Ikeda-Fujii-Fujita sum rule value is quenched by 6% owing to relativistic effects. The quenched amount is taken by the nucleon-antinucleon states. This fact, together with the recent experiment which has observed 90% of the sum rule value, implies that the contribution of the Δ-hole states to the quenching is strongly reduced. As a result, the Landau-Migdal parameter g'NΔ which dominates the critical density of the pion condensation becomes much smaller than what was believed before