Unitarity sum rules and soft-pion amplitudes

C. Rosenzweig, G. Veneziano

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We examine unitarity bounds on scattering amplitudes by using « unitarity sum rules » at high energy. Threshold conditions emerge when certain mass parameters approach zero. For ππ scattering a bound similar to (but somewhat weaker than) the Adler condition is shown to be needed in order to avoid a dangerous mass (infra-red) singularity. A different argument, which uses crucially the pseudoscalar nature of the pion and a few very plausible dynamical assumptions, yields a stronger bound as well as the possibility of extension to general pion amplitudes. We finally discuss our results as well as the possibility of understanding spontaneously broken symmetries from general S-matrix principles.

Original languageEnglish (US)
Pages (from-to)409-424
Number of pages16
JournalIl Nuovo Cimento A Series 11
Issue number2
StatePublished - Nov 1972
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Nuclear and High Energy Physics
  • Astronomy and Astrophysics


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