Relativistic Mean-Field Theory with Pion in Finite Nuclei

First we review the present relativistic mean-field theory from the view point of the missing pion contribution. Then we discuss the role played by pions in hadrons and light nuclei. We introduce the interesting experimental data on pionic states taken at RCNP. These data seem to suggest the occurrence of surface pion condensation in finite nuclei. We show the results of the relativistic mean-field theory with the pion. We find that the pion mean-field becomes finite with a reasonable parameter choice. A qualitative discussion is presented on the consequence of a finite pion mean-field on Gamow-Teller transitions and spin response functions as well as other quantities.