Lightest scalars as chiral partners of the Nambu–Goldstone bosons

We review the spectrum of lightest scalar resonances recently determined using dispersion techniques. The conceptual difference between the pole mass and the bare mass (or the line–shape mass) is stressed. The nature of the lightest scalars are discussed and we argue, without relying on any model details, that the σ(500), κ(700), a0(980) and f0(980) may be understood as chiral partners of the Nambu–Goldstone bosons in the linear realization of chiral symmetry. But there remains some difficulties in understanding the role of f0(980) in this picture.