Summary
An explicit solution of the differential equation for Weinberg’s class of chiral Lagrangians, with arbitraryf(π 2), is given here. On the contrary, for any given symmetry-breaking term the explicit solution of the correspondingf(π 2) is not found. We also construct here a chiral Lagrangian which has the advantage of satisfying the «special» PCAC and of being independent of field redefinition and further the corresponding explicit solution off(π 2) is found. Two examples, corresponding toN=1, 2 in Weinberg’s class are discussed. The π-π scattering lengths calculated from our proposed Lagrangian agree with Schwinger’s results.
Riassunto
Si presenta una soluzione esplicita dell’equazione differenziale per la classe di Weinberg delle lagrangiane chirali, conf(π 2) arbitrario. Per un termine qualunque che rompa la simmetria, invece, non si è trovata la soluzione esplicita della corrispondentef(π 2). Si costruisce anche una lagrangiana chirale che ha il vantaggio di soddisfare la PCAC «speciale» e di essere indipendente dalla ridefinizione del campo; si trova inoltre la corrispondente soluzione esplicita dif(π 2). Si discutono due esempi corrispondenti adN=1, 2 nella classe di Weinberg. Le lunghezze di scattering π-π ottenute con la lagrangiana proposta in questo articolo concordano con i risultati di Schwinger.
Реэюме
В работе приводится точное рещение дифференциального уравнения для Вейнберговского класса чиральных лагранжианов, с проиэвольнымf(π 2). Однако, для любого эаданного члена, нарущаюшего симметрию, точное рещение для соответствуюшегоf(π 2) не найдено. Мы также конструируем чиральный лагранжиан, который имеет то преимушество, что удовлетворяет « специальной » PCAS и не эависит от нового определения поля. Затем находится соответствуюшее точное рещение дляf(π 2). Обсуждаются два примера, соответствуюшиеN=1,2 в классе Вейнберга. Вычисленные длины π-π рассеяния, исходя иэ предложенного нами лагранжиана, согласуются с реэультатами Щвингера.
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References
W. A. Bardeen andB. W. Lee: inNuclear and Particle Physics, edited byB. Margolis andC. S. Lam (New York, 1968).
S. Weinberg:Phys. Rev.,166, 1568 (1968).
A special case has been considered byW. Sollfrey:Phys. Rev.,173, 1805 (1968).
We have recently become aware of a different form obtained byS. P. Rosen, which is also independent of the definition of the pion field;The relationship between nonlinear and linear realizations of chiral SU2 × SU2,Purdue University preprint (1970).
J. Schwinger:Phys. Rev.,167, 1432 (1968).
See,e.g.,L. Brand:Differential and Difference Equations (New York, 1966).
The symmetry-breaking term is chosen to be just the pion mass term without any higher-order term inπ 2.W. F. Long andJ. S. Kovacs:Phys. Rev. D,1, 1333 (1970).
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Liu, C.J., Chow, Y. Chiral Lagrangians and pion-field redefinition. Nuov Cim A 1, 369–375 (1971). https://doi.org/10.1007/BF02723267
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DOI: https://doi.org/10.1007/BF02723267