منابع مشابه
Nucleon mass and pion loops : Renormalization †
Using Dyson–Schwinger equations, the nucleon propagator is analyzed nonperturbatively in a field–theoretical model for the pion–nucleon interaction. Infinities are circumvented by using pion–nucleon form factors which define the physical scale. It is shown that the correct, finite, on–shell nucleon renormalization is important for the value of the mass–shift and the propagator. For physically a...
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We discuss the evaluation of the nucleon isoscalar axial coupling, g (0) A , in the in-stanton vacuum, using the 1/N c expansion. This approach allows a fully consistent treatment of the U (1) A anomaly. We compute the nucleon matrix element of the topological charge density, N |F F |N , and show that it reduces to the matrix element of the divergence of the isoscalar axial quark current. Our a...
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The real and imaginary part of the vacuum polarisation function Π(q2) induced by a massive quark is calculated in perturbative QCD up to order αs. The method is described and the results are presented. This extends the calculation by Källén and Sabry from two to three loops. The complete postscript file of this preprint, including figures, is available via anonymous ftp at ttpux2.physik.uni-kar...
متن کاملThe QED vacuum polarization function at four loops and the anomalous magnetic moment at five loops
The anomalous moment of the muon is one of the most fundamental observables. It has been measured experimentally with a very high precision and on theory side the contributions from perturbative QED have been calculated up to five-loop level by numerical methods. Contributions to the muon anomalous magnetic moment from certain diagram classes are also accessible by alternative methods. In this ...
متن کاملSparseness, Immanence, and Naturalness
In the past fifteen years or so there has been a lot of attention paid to theories of “sparse” universals, particularly because of the work of D. M. Armstrong. These theories are of particular interest to those of us concerned with the distinction between natural and non-natural properties, since, as David Lewis has observed, it seems possible to analyze naturalness in terms of sparse universal...
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ژورنال
عنوان ژورنال: Nuclear Physics A
سال: 1997
ISSN: 0375-9474
DOI: 10.1016/s0375-9474(97)00062-6