Current commutators in the hadronic vacuum ande+e−annihilation

We study the behavior of current commutators in the vacuum within the quark-gluon theory of strong interactions. Especially, the problem of S${\mathrm{U}}_3$ × S${\mathrm{U}}_3$ symmetry breaking is considered. We derive spectral-function sum rules involving the bare quark masses. Applications to vector-meson dominance, $K_{l3}$ decay, and $e^{+}{e}^{-}$ annihilation are discussed.