Comment on `A simple explanation of the non-appearance of physical gluons and quarks'

In a recent paper by Johan Hansson [hep-ph/0208137] it is claimed that the non-appearance of quarks and gluons as physical particles is an automatic result of the nonabelian nature of the color interaction in quantum chromodynamics. It is shown that the arguments given by Hansson are insufficient to support his claim by giving simple counter arguments.Comment: 3 pages, LATE

Aspects of the derivative coupling model in four dimensions

A concise discussion of a 3+1-dimensional derivative coupling model, in which a massive Dirac field couples to the four-gradient of a massless scalar field, is given in order to elucidate the role of different concepts in quantum field theory like the regularization of quantum fields as operator valued distributions, correlation distributions, locality, causality, and field operator gauge transformations.Comment: 17 pages, LaTeX, corresponding to the published versio

Bound-free pair production cross section in heavy-ion colliders from the equivalent photon approach

Exact calculations of the electron-positron pair production by a single photon in the Coulomb field of a nucleus with simultaneous capture of the electron into the K-shell are discussed for different nuclear charges. Using the equivalent photon method of Weizsaecker and Williams, a simple expression for the bound-free production of electron-positron pairs by colliding very-high-energy fully stripped heavy ions is derived for nuclei of arbitrary charge.Comment: 4 pages, 2 figures, style file include

Coulomb distortion effects in quasi-elastic (e,e') scattering on heavy nuclei

The influence of the Coulomb distortion for quasi-elastic (e,e') scattering on highly charged nuclei is investigated in distorted wave Born approximation for electrons. The Dirac equation is solved numerically in order to obtain exact electron continuum states in the electrostatic field generated by the charge distribution of an atomic nucleus. Different approximate models are used to describe the nucleon current in order to show that, at high electron energies and energy-momentum transfer, the influence of Coulomb distortions on (e,e') cross sections can be reliably described by the effective momentum approximation, irrespective of details concerning the description of the nuclear current.Comment: 34 pages, 11 figures, LATEX, style file include

Scalar models of formally interacting non-standard quantum fields in Minkowski space-time

For decades, a lot of work has been devoted to the problem of constructing a non-trivial quantum field theory in four-dimensional space time. This letter addresses the attempts to construct an algebraic quantum field theory in the framework of non-standard theories like hyperfunction or ultra-hyperfunction quantum field theory. For this purpose model theories of formally interacting neutral scalar fields are constructed and some of their characteristic properties like two-point functions are discussed. The formal self-couplings are obtained from local normally-ordered analytic redefinitions of the free scalar quantum field, mimicking a non-trivial structure of the resulting Lagrangians and equations of motion.Comment: 4 pages, 6 references and a conclusion section added, abstract slightly modifie

Coulomb solutions from improper pseudo-unitary free gauge field operator translations

Fundamental problems of quantum field theory related to the representation problem of canonical commutation relations are discussed within a gauge field version of a van Hove-type model. The Coulomb field generated by a static charge distribution is described as a formal superposition of time-like pseudo-photons in Fock space with a Krein structure. In this context, a generalization of operator gauge transformations is introduced to generate coherent states of abelian gauge fields interacting with a charged background.Comment: 19 pages, two sections extende