Interactivity: A review of the concept and a framework for analysis

The terms `interactivity' and `interactive media' became significant buzz-words during the late 1980s and early 1990s when the multi-media euphoria fascinated politicians, economists, and researchers alike. However, right from the beginning of the scientific debate, the inconsistent usage of the term `interactivity' massively complicated the comparability of numerous empirical studies. This is where this article joins the discussion. First, the article sheds light on the terminological origins of `interactivity' and distinguishes the term from cognate expressions. Further, it restructures and extends existing findings on the basis of a new analysis framework which considers three levels of interactive communication (action level, level of subjective situation evaluation, and level of meaning exchange). Finally, it delivers a systematic overview of specific criteria of interactive communication

The Pion-Cloud Contribution to the Electromagnetic Nucleon Form Factors

We study the electromagnetic structure of the nucleon within a hybrid constituent-quark model that comprises, in addition to the $3q$ valence component, also a $3q$+$\pi$ non-valence component. To this aim we employ a Poincar\'e-invariant multichannel formulation based on the point-form of relativistic quantum mechanics. With a simple 3-quark wave function for the bare nucleon, i.e. the $3q$-component, we obtain reasonable results for the nucleon form factors and predict the meson-cloud contribution to be significant only below $Q^2\lesssim 0.5$\,GeV$^2$ amounting to about 10\% for $Q^2\rightarrow 0$, in accordance with the findings of other authors.Comment: Contribution presented by W. Schweiger at the 21st International Conference on Few-Body Problems in Physics, Chicago IL, May 18-22, 2015; 4 pages, 2 figure

Hard exclusive photoproduction of charmed mesons

{We investigate the photoproduction process $p \gamma \rightarrow \Lambda_{c}^{+} \overline{D^{0}}$ within the handbag approach, which we assume to be the dominant mechanism at energies well above the production threshold and in the forward scattering hemisphere.Comment: proceedings of Photon 2013, May 20-24 2013, Paris, Franc