On the nature of the lightest scalar resonances
  We briefly review the recent progresses in the new unitarization approach being developed by us. Especially we discuss the large $N_c$ $\pi\pi$ scatterings by making use of the partial wave $S$ matrix parametrization form. We find that the $\sigma$ pole may move to the negative real axis on the second sheet of the complex $s$ plane, therefore it raises the interesting question that this `$\sigma$' pole may be related to the $\sigma$ in the linear $\sigma$ model. 
Z. X. Sun, L. Y. Xiao, Z. G. Xiao, H. Q. Zheng, Z. Y. Zhou