Algebraic Structure of Current Algebra, Superconvergence Sum Rules, and the Infinite-Momentum Method

We present here a derivation of Weinberg's formulas for the algebraic structure of current algebra and superconvergence sum rules in the case of massive pions, using the infinite-momentum method. We show that Weinberg's formulas are closely related to the fact that there is no $T=2\mathrm{}$ part in some double commutation relations between axial charges ${Q_5}^a$, ${Q_5}^b$ and the generators of inhomogeneous Lorentz transformations.