Summary
We study various effects associated with Euclidean instanton solutions. By means of an instructive example, we discuss how the probability of tunnelling among vacuum states in Minkowski space is connected with stationary (instanton) solutions in Euclidean space. Next we examine the cluster decomposition properties of non-Abelian gauge theories and indicate how these are recovered in the presence of instanton solutions. The validity of perturbation theory in these field theories is discussed. We show that perturbative analyses are only tenable in the deep Euclidean region, unless there is an intrinsic scale. Finally, we examine the role that instantons have in providing violations of otherwise conserved quantum numbers. We study, in particular, how fermion number nonconservation results by a careful examination of the path integral for the fermion-generating functional.
Riassunto
Si studiano i vari effetti associati con le soluzioni istantoniche euclidee. Per mezzo di un esempio istruttivo, si discute in che modo la probabilità di tunnel tra stati vuoti nello spazio di Minkowski è collegata con soluzioni stazionarie (istantoni) nello spazio euclideo. Quindi si esaminano le proprietà di decomposizione degli ammassi di teorie di gauge non abeliane e si indica come esse siano ripristinate in presenza di soluzioni istantoniche. Si discute la validità della teoria delle perturbazioni in queste teorie di campo. Si mostra che analisi perturbative sono sostenibili solo nella regione euclidea profonda, a meno che non ci sia una scala intrinseca. Infine si esamina il ruolo che hanno gli istantoni nel fornire violazioni degli altrimenti conservati numeri quantici. Si studia, in particolare, come risulti la non conservazione del numero di fermioni per mezzo di un attento esame dell’integrale del percorso per il funzionale di generazione dei fermioni.
Реэюме
Мы исследуем раэличные зффекты, свяэанные с звклидовыми « инстантонными» рещениями. На примере мы покаэываем, как вероятность туннелирования между вакуумными состояниями в пространстве Минковского свяэана со стационарными (« инстантонными ») рещемиями в звклидовом пространстве. Затем мы иэучаем свойства распада кластеров для неабелевых калибровочных теорий. Мы покаэываем, как зти теории восстанавливаются при наличии «инстантонных» рещений. Обсуждается справедливость теории воэмушений в зтих теориях полей. Мы покаэываем, что пертурбационный аналиэ является справедливым в звклидовой области, если не сушествует внутреннего масщтаба. В эаключение, мы исследуем роль, которую играют «инстантоны» при нарущениях сохраняюшихся квантовых чисел. В частности, мы исследуем, как воэникает несохранение числа фермионов в реэультате тшательного исследования интеграла по траектории для фермионного обраэуюшего функционала.
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References
A. A. Belavin, A. M. Polyakov, A. S. Schwartz andYu. S. Tyupkin:Phys. Lett.,59 B, 85 (1975).
A. M. Polyakov:Phys. Lett.,59 B, 82 (1975).
G. ’t Hooft:Phys. Rev. Lett.,37, 8 (1976).
R. Jackiw andC. Rebbi:Phys. Rev. Lett.,37, 172 (1976).
C. G. Callan, R. F. Dashen andD. J. Gross:Phys. Lett.,63 B, 334 (1976).
G. ’t Hooft:Phys. Rev. (in press).
J. L. Gervais, A. Jevicki andB. Sakita:Phys. Rev.,12, 1038 (1975);E. Tomboulis:Phys. Rev. D,12, 1678 (1975).
In fact, to evaluate the contribution even of our restricted set of functions (24), we would have to allow all possible functionsF. The question of whether or not these terms are significant in the integral then depends on whether the overall divergences which arise are of the same order as those of theq = 0 terms. We do not investigate this question here. It has been discussed by’t Hooft (ref. (6)) for the instanton solutions.
In a recent preprint,Gervais andSakita (ref. (8)) discuss this point further. They attempt to write in Minkowski space the field configuration of the Euclidean instanton solution and examine the relevant tunnelling problem. Their procedure is extremely convoluted, but eventually arrives at the expected answer. Our example, hopefully, emphasizes the simpler physical aspects of the problem.
J. L. Gervais andB. Sakita: CCNY preprint (CCNY-HEP-76 11).
A. de Rujula andH. Georgi:Phys. Rev. D,13, 1296 (1976);E. C. Poggio, H. R. Quinn andS. Weinberg:Phys. Rev. D,13, 1958 (1976).
T. Kinoshita:Journ. Math. Phys.,3, 650 (1962);T. Kinoshita andA. Ukawa:Phys. Rev. D,13, 1573 (1976).
See, for example,S. L. Adler:Lectures at the 1970 Brandeis Summer Institute, edited byS. Deser, M. Grisaru andH. Pendleton (Cambridge, Mass., 1970).
S. Weinberg:Phys. Rev. Lett.,19, 1264 (1967);A. Salam: inElementary Particle Physics: Relativistic Groups and Analyticity (Nobel Symposium No. 8), edited byN. Svartholm (Stockholm, 1968).
The integrals over dλ and d4 z re-establish scale and translation invariance for the fermion Green’s function (see,e.g., ref. (6)).
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Work supported in part by NSF grants PHY 75-18444 and MPS 75-20427.
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Peccei, R.D., Quinn, H.R. Some aspects of instantons. Nuov Cim A 41, 309–330 (1977). https://doi.org/10.1007/BF02730110
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DOI: https://doi.org/10.1007/BF02730110