Summary
It is well known that for graphs with six external lines or more, the necessary linear dependence of any five external 4-vectors imposes certain conditions on the Mandelstam variabless ij =(P i +P j )2. The purpose of this note is to point out that these conditions in general lead to kinematic branch points when the graph is considered as usual as an analytic function of its independent variables.
Riassunto
È ben noto che, per grafici con sei o più linee esterne, la necessaria dipendenza lineare di ogni gruppo di cinque quadrivettori interni impone alcune condizioni alle variabili di Mandelstams ij =(P i +P j )2. Lo scopo di questa nota è di mettere in evidenza che queste condizioni in generale conducono a punti di ramificazione cinematici, quando il grafico viene considerato, come di solito, una funzione analitica delle sue variabili indipendenti.
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Literatur
The number 3n−10 can be arrived at by simple group theoretical methods. I am grateful to Mr.J. Cunningham (Edinburgh) and Dr.S. Ishihara (Tokyo and Hong Kong) for pointing this out to me.
Chan Hong-Mo: (1961), to be published.
The reader is reminded of the more familiar case of the threshold branch points See,e.g. R. E. Peierls:Proc. Roy. Soc., A253, 16 (1959);Chan Hong-Mo:Proc. Roy. Soc., A261, 329 (1961).
E.g. G. Chew andS. Mandelstam:Phys. Rev.,119, 1121 (1960).
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Hong-Mo, C. New class of kinematic branch points forn-line graphs. Nuovo Cim 23, 181–185 (1962). https://doi.org/10.1007/BF02733553
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DOI: https://doi.org/10.1007/BF02733553