The connection between the Feynman triangle diagram and the light-front formalism for spin-0 and spin-1 two-fermion systems is analyzed. It is shown that in the limit q+ = 0 the form factors for both spin-0 and spin-1 systems can be uniquely determined using only the good amplitudes, which are not affected by spurious effects related to the loss of rotational covariance present in the light-fro...

The method of using Hopf algebras for calculating Feynman integrals developed by Abreu et al. is applied to the two-loop nonplanar on-shell diagram with massless propagators and three external mass scales. We show that existence cut diagrams comprising coproduct, first entry condition integrability was found be true planar case also holds case; furthermore, symbol alphabet same as case. This on...

The form factor of hadronic systems in various forms of relativistic quantum mechanics is considered. Motivated by the agreement of the nucleon “point-form” results with experiment, results for a toy model corresponding to the simplest Feynman diagram are first presented. These ones include the results for this diagram, which plays the role of an experiment, for the front-form and instant-form ...

In the framework of causal perturbation theory, it is possible to avoid ultraviolet divergences in the calculation of Feynman diagrams from the start, making subsequent regularization of divergent diagrams unnecessary. We give a simple introduction to the most important calculational features of the method. The method is also applied to the ’divergent’ general massive two-loop sunrise selfenerg...

In this contribution the matrix element generator AMEGIC++ will be presented. It automatically generates Feynman diagrams, helicity amplitudes, and suitable phase space mappings for processes involving multi-particle final states within the Standard Model and some of its popular extensions. Due to the rising energy frontier in high-energy collider experiments, potential signals and their backgr...

The problem of perturbative renormalization theory is to give a meaning to certain divergent integrals arising from Feynman diagrams. The analytical difficulty is to regularize the occurring divergent integrals, associating to each Feynman diagram some finite value. The physical difficulty is to do this in such a way that the outcome has a physical meaning. The contributions of the various Feyn...

A modular application of the integration by fractional expansion method for evaluating Feynman diagrams is extended to diagrams that contain loop triangle subdiagrams in their geometry. The technique is based in the replacement of this module or subdiagram by its corresponding multiregion expansion (MRE), which in turn is obtained from Schwinger’s parametric representation of the diagram. The r...

Chiral gauge anomalies on noncommutative Minkowski Space-time are computed and have their origin elucidated. The consistent form and the covariant form of the anomaly are obtained. Both Fujikawa's method and Feynman diagram techniques are used to carry out the calculations. 1 Written version of the invited lecture given at the Euroconference " Brane New World and Noncommutative Geometry " , Vil...