Summary
The analytic properties of perturbation theory amplitudes written as integrals over internal invariants are discussed. Single-loop amplitudes are considered and a condition, equivalent to the positive α condition, is derived for singularity in the physical limit. Some simple double-loop diagrams are discussed also and the existence and nature of a certain mixed second-type singularity is investigated. A feature of these latter diagrams is the necessity of dealing with spurious singularities. The relevance of these considerations to certain three-particle phasespace integrals is pointed out.
Riassunto
Si discutono le proprieetà analitiche delle ampiezze nella teoria della perturbazione corne integrali delle variabili interne. Si prendono in considerazioni ampiezze con una sola ansa e se ne deduce una condizione, equivalente alla condizione dell’a positivo, per la singolarità nel limite fisico. Si discutono anche alcuni diagrammi semplici con doppia ansa e si indaga sull’esistenza e la natura di una certa singolarità mista di secondo tipo. Una caratteristica di questi diagrammi è la necessità di trattare singolarità spurie. Si mette in rilievo l’importanza di queste considerazioni per alcuni integrali dello spazio delle fasi a tre particelle.
Similar content being viewed by others
References
A comprehensive set of references can be found in the lectures of R. J. Eden and J. C. Polkinghorne :Lecture Notes of the Brandeis Summer Institute, vol.1 (New York, 1961).
R. E. Cutkosky:Journ. Math. Phys.,1, 429 (1960).
R. J. Eden:Proc. Roy. Soc. (London), A210, 388 (1952).
J. C. Polkinghorne:Nuovo Cimento,23, 360 (1962);25, 901 (1962).
H. P. Stapp:Phys. Rev.,125, 2139 (1962).
D. I. Olive:Analytic Continuation of the Scattering Amplitude Through a Three-Particle Out (Cambridge preprint).
D. B. Fairlie, P. V. Landshoff, J. Nuttall andJ. C. Polkinghorne:Journ. Math. Phys.,3, 594 (1962).
I. T. Drummond:Nuovo Cimento,24, 248 (1962).
M. Fowler:Journ. Math. Phys.,3, 936 (1962);Second-Type Singularities in Perturbation Theory (Cambridge preprint).
M. Fowler, P. V. Landshoff andR. Lardner:Nuovo Cimento,17, 959 (1960).
L. M. Brown:Nuovo Cimento,22, 178 (1961).
Author information
Authors and Affiliations
Additional information
The research reported in this document has been sponsored in part by the Air Force Office of Scientific Research, OAR, through the European Office, Aerospace Research, United States Air Force.
Rights and permissions
About this article
Cite this article
Drummond, I.T. Singularities of Feynman amplitudes. Nuovo Cim 29, 720–741 (1963). https://doi.org/10.1007/BF02827793
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02827793