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A Critical Examination to the Unitarized Scattering Chiral Amplitudes
We discuss the Pad\'e approximation to the scattering amplitudes in
1--loop chiral perturbation theory. The approximation restores unitarity and
can reproduce the correct resonance poles, but the approximation violates
crossing symmetry and produce spurious poles on the complex plane and
therefore plagues its predictions on physical quantities at quantitative level.
However we find that one virtual state in the IJ=20 channel may have physical
relevance.Comment: 13 pages + 4 eps figures submit to Commun. Theor. Phy
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