Interactions in three coupled channels: pi-pi, K-anti K and sigma-sigma have
been investigated in a wide two-pion effective mass region from the pi-pi
threshold up to 1600 MeV. Analytical structure of amplitudes in all channels
has been studied. It was shown that its knowledge is necessary to understand
spectrum of scalar mesons and their nature.Comment: 6 pages, Invited talk at YITP Workshop on Possible Existence of the
sigma meson and it Implications to Hadron Physics (sigma-meson 2000), Kyoto,
Japan, 12-14 Jun 200
