Showing papers on "Vertex function published in 1989"
TL;DR: An electromagnetic current operator is deduced from the most general form of the extended pion-nucleon vertex function using the minimal substitution prescription and it is proved that the sum of the obtained current operator and the isolated-pole contribution satisfies the Ward-Takahashi identity derived for the pion photoproduction.
Abstract: An electromagnetic current operator is deduced from the most general form of the extended pion-nucleon vertex function using the minimal substitution prescription. It is proved that the sum of the obtained current operator and the isolated-pole contribution satisfies the Ward-Takahashi identity derived for the pion photoproduction. The minimal-coupling interaction is applied to the calculation of the one-pion exchange current regularized by the pion-nucleon form factors. It is found that the one-pion exchange current operator including hadronic and electromagnetic form factors satisfies the Ward-Takahashi equation for the nucleon-nucleon interaction.
49 citations
TL;DR: In this paper, the single impurity Anderson model is studied for finite values of the Coulomb interaction U between two f-electrons, and the resulting equations are solved numerically properly treating both energy variables of the vertex function.
24 citations
22 citations
TL;DR: In this article, the vertex functions of the Neveu-Schwarz sector were obtained for the first four mass levels and coincide with those in the operator formalism for orientable closed strings.
15 citations
TL;DR: The cutoff dependence of the gauge coupling α to all orders in perturbation theory for a quenched QED scenario by stability analysis of the CJT effective potential was determined in this article.
11 citations
TL;DR: In this article, the authors investigated the Schwinger-Dyson equation for the quark propagator with the help of the corresponding Slavnov-Taylor identity in the infrared region. And they obtained an infrared finite quark propagation model with no pole and satisfying the chiral symmetry breaking condition.
10 citations
TL;DR: In this article, it was shown that the generalized Ward identity (GWI) implies the existence of relationships between the different statistical moments and the response functions to external forces in a hydrodynamic system described by the Navier-Stokes equations.
9 citations
TL;DR: In this paper, the effect of the finite electromagnetic correction to the quark-gluon vertex function in color singlet bound states is investigated. But the model is restricted to the standard model of the strong and electroweak interactions.
8 citations
TL;DR: The Lorentz-noninvariant divergent structures (local as well as nonlocal ones) turn out to be proportional to the classical equations of motion.
Abstract: We apply the Leibbrandt-Mandelstam prescription to QCD within a family of gauges comprising the homogeneous axial gauge and the planar gauge. We calculate to one-loop order the UV-divergent parts of the quark self-energy, the quark-quark-gluon vertex, and the four-quark one-particle-irreducible vertex. The results are found to satisfy the Slavnov-Taylor-Lee identity. Summing up the contributions to the {ital S}-matrix element for quark-quark scattering, we show that the result is indeed independent of the gauge parameters {ital n}{sub {mu}} and {alpha} and of the auxiliary vector {ital n}{sub {mu}}{sup *}. The nonlocal counterterms persisting in Green's functions for {ital n}{sup 2}{ne}0 are thus compatible with gauge independence of physical quantities. The Lorentz-noninvariant divergent structures (local as well as nonlocal ones) turn out to be proportional to the classical equations of motion.
6 citations
TL;DR: In this article, a gauge-invariant nonperturbative approach to the bound-state problem within the infrared-finite Bethe-Salpeter equation is presented, which can be directly applied to the generalized ladder approximation of this equation.
2 citations