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H. D. Dahmen

Publications and source records attributed to H. D. Dahmen.

9 recordsLinked to original sources
arXiv2000

Multi-channel Bethe-Salpeter equation

A general form of multi-channel Bethe-Salpeter equation is considered. In contradistinction to the hitherto applied approaches, our coupled system of equations leads to the simultaneous solutions for all relativistic four-point Green functions (elastic and inelastic) appearing in a given theory. A set of relations which may be helpful in approximate treatments is given. An example of extracting useful information from the equations is discussed: we consider the most general trilinear coupling of N different scalar fields and obtain - in the ladder approximation - closed expressions for the Regge trajectories and their couplings to different channels in the vicinity of l = -1. Sum rules and an example containing non-obvious symmetry are discussed.

hep-th↗
arXiv1998

Quantile motion of electromagnetic waves in wave guides of varying cross section and dispersive media

We discuss applications of the quantile concept of trajectories and velocities to the propagation of electromagnetic signals in wave guides of varying cross section. Quantile motion is a general description of the transport properties of measurable conserved quantities in quantum mechanics as well as in classical electrodynamics. In the latter case we consider the quantile motion of electromagnetic energy as the direct result of a physical measurement. In this sense the quantile velocity corresponds to the electromagnetic signal velocity also in the presence of barriers and inhomogeneities in the medium of propagation. We show that this signal velocity is always smaller than the speed of light in vacuum. Using numerical examples we demonstrate how typical wave phenomena can be described in terms of the quantile motion.

physics.class-ph↗
arXiv1998

Quantile Motion and Tunneling

The concepts of quantile position, trajectory, and velocity are defined. For a tunneling quantum mechanical wave packet, it is proved that its quantile position always stays behind that of a free wave packet with the same initial parameters. In quantum mechanics the quantile trajectories are mathematically identical to Bohm's trajectories. A generalization to three dimensions is given.

quant-ph↗
arXiv1998

Grand Unified Theories in Superstrings in the Free World-Sheet Fermion Formulation

In the framework of the four dimensional heterotic superstring with free world-sheet fermions we study the GUSTs which contain non-abelian horizontal symmetry. To solve the problem of breaking the G_GUT gauge symmetry of the level one current algebra we extend the gauge symmetry to G x G. Using the autoduality of the fermionic charge lattice we study the possibilities of constructing of some GUST gauge groups. We also study the string amplitudes and for one realistic model explicitly calculate the renormalizable and non-renormalizable (N=4,5,6) contributions to the superpotential. We observe that the existence of the mass matrix ansatz depends on the way of the breaking of the horizontal gauge symmetry.

hep-th↗
arXiv1997

Collinear Asymptotic Dynamics for Massive Particles. Multi-Channel Regge Behaviour

The high-energy behaviour in a multi-channel system is investigated in the framework of collinear asymptotic dynamics for massive particles. We consider the most general trilinear coupling of N different scalar fields. We find Regge behaviour and obtain closed expressions for the Regge trajectories and couplings. The results are corraborated in the multi-channel Bethe-Salpeter approach. The scattering processes dominated by single Regge trajectories are explicitly given.

hep-ph↗
arXiv1996

Topological Yang-Mills Theory with Two Fermionic Charges. A Superfield Approach on Kähler Manifolds

The four-dimensional topological Yang-Mills theory with two anticommuting charges is naturally formulated on Kähler manifolds. By using a superspace approach we clarify the structure of the Faddeev-Popov sector and determine the total action. This enables us to perform perturbation theory around any given instanton configuration by manifestly maintaining all the symmetries of the topological theory. The superspace formulation is very useful for recognizing a trivial observable (i.e. having vanishing correlation functions only) as the highest component of a gauge invariant superfield. As an example of non-trivial observables we construct the complete solution to the simultaneous cohomology problem of both fermionic charges. We also show how this solution has to be used in order to make Donaldson's interpretation possible.

hep-th↗
arXiv1994

Collinear Asymptotic Dynamics for Massive Particles. Reggeization and Eikonalization

The dynamics of massive particles in the collinear high momentum regime is investigated. Methods hitherto exploiting large time asymptotic Hamiltonians in the Dirac picture for the treatment of infrared divergences are adapted to the collinear asymptotic dynamics. The essential role of time ordering of the dressing operators is brought out.

hep-th↗
arXiv1993

A Monte Carlo Event Generator for W Off-shell Pair Production including Higher Order Electromagnetic Radiative Corrections

We present the Monte Carlo event generator {\tt WOPPER} for pair production of $W$'s and their decays at high energy $e^+e^-$ colliders. {\tt WOPPER} includes the effects from finite $W$ width and focusses on the calculation of higher order electromagnetic corrections in the leading log approximation including soft photon exponentiation and explicit generation of exclusive hard photons.

hep-ph↗