S>Convergence of the expansion of the cosine dependence of the amplitude ; employed in the deduction of the integral equations from the Mandelstam ; representation is investigated in the case of pi - pi scattering. An equation ; set for low energies is presented in which rapid convergence of the expansion of ; the real part of the amplitude can be attained by a conformal mapping of the ; cosine
... [Show full abstract] plane. Since any power of the function employed contains an infinite ; number of partial waves this approach should be especially convenient in those ; cases when high number waves may be important.;