A relativistic coupled-channel formalism for the pion form factor

The electromagnetic form factor of a confined quark-antiquark pair is calculated within the framework of point-form relativistic quantum mechanics. The dynamics of theexchanged photon is explicitly taken into account by treating theelectromagnetic scattering of an electron by a meson as a relativistic two-channel problem for a Bakamjian-Thomas type mass operator. This approach guarantees Poincare invariance. Using a Feshbach reduction the coupled-channel problem can be converted into a one-channel problem for the elastic electron-meson channel. By comparing the one-photon-exchange optical potential at the constituent and hadronic levels, we are able to unambiguously identify the electromagnetic meson form factor. Violations of cluster-separability properties, which are inherent in the Bakamjian-Thomas approach, become negligible for sufficiently large invariant mass of the electron-meson system. In the limit of an infinitely large invariant mass, an equivalence with form-factor calculations done in front-form relativistic quantum mechanics is established analytically.Comment: 3 pages, 1 figure, submitted to EPJ Web of Conference

Witten index, axial anomaly, and Krein's spectral shift function in supersymmetric quantum mechanics

A new method is presented to study supersymmetric quantum mechanics. Using relative scattering techniques, basic relations are derived between Krein’s spectral shift function, the Witten index, and the anomaly. The topological invariance of the spectral shift function is discussed. The power of this method is illustrated by treating various models and calculating explicitly the spectral shift function, the Witten index, and the anomaly. In particular, a complete treatment of the two‐dimensional magnetic field problem is given, without assuming that the magnetic flux is quantized

Cost Evaluation for Traffic and Transport Infrastructure Projects Taking Account of Project Risks

The realisation of large transport infrastructure projects is influenced by a wide range of different factors. The general expectation that a project should be carried out under defined boundary conditions within the planned period and on budget requires a high level of design, planning and controlling. This paper discusses standardised comprehensible fundamental rules and guidelines for defining project costs and project budgets of infrastructure projects taking into account risk assessment and risk management. Adhering to these guidelines and rules contributes to ensure that the structure can be built in the required quality, on schedule and on budget, as well as to estimate the predicted margin of the budget. The paper is based on the ÖGG Guideline ”Kostenermittlung für Verkehrsinfrastrukturprojekte unter Berücksichtigung relevanter Projektrisiken“ (Cost Estimation of Traffic Infrastructure Projects in Consideration of Relevant Projects Risks) published in 2005. The authors of the present paper chaired the working group responsible for the guideline. The main objective of this paper is to develop an adequate structure of cost in terms of basic costs and risk costs. For the evaluation of risk costs two different methods are described in detail: The deterministic method of risk cost evaluation is based on a certain percentage of the basic costs which is sufficient for simple projects. For complex projects a qualitative risk cost evaluation based on identified risk scenarios is necessary to get a sound basis of the budgeting of the project

Polynomial Solutions of Generalized Quartic Anharmonic Oscillators

We introduce a nilpotent group to write a generalized quartic anharmonic oscillator Hamiltonian as a polynomial in the generators of the group. Energy eigenvalues are then seen to depend on the values of the two Casimir operators of the group. This dependence exhibits a scaling law which follows from the scaling properties of the group generators. Demanding that the potential give rise to polynomial solutions in a particular Lie algebra element puts constraints on the four potential parameters, leaving only two of them free. For potentials satisfying such constraints at least one of the energy eigenvalues and the corresponding eigenfunctions can be obtained in closed analytic form; examples, beyond those available in the literature, are given. Finally, we find solutions for particles in external electromagnetic fields in terms of these quartic polynomial solutions.Comment: 22 pages, 5 figure

Statistical model of the powder flow regulation by nanomaterials

Fine powders often tend to agglomerate due to van der Waals forces between the particles. These forces can be reduced significantly by covering the particles with nanoscaled adsorbates, as shown by recent experiments. In the present work a quantitative statistical analysis of the effect of powder flow regulating nanomaterials on the adhesive forces in powders is given. Covering two spherical powder particles randomly with nanoadsorbates we compute the decrease of the mutual van der Waals force. The dependence of the force on the relative surface coverage obeys a scaling form which is independent of the used materials. The predictions by our simulations are compared to the experimental results.Comment: 18 pages, 9 figures, 1 table, LaTeX; reviewed version with minor changes, published (Powder Technology