Granular electrostatics: Progress and outstanding questions

Every physicist studies electrostatics in the first year of graduate study, and learns that the electric field is a linear superposition of contributions from charges, each of which obeys a 1/r2 law. Every physicist also studies classical mechanics, and learns that the problem of three or more bodies in a 1/r2 field is intrinsically nonlinear. The contradiction between these two teachings is seldom commented upon. In this paper, I overview what is known, what is believed, and what remains entirely unknown about the behaviors of multiple electrically polarized or charged particles. I show that the nonlinearity recognized in classical mechanics leads to highly complex dynamics when particles are permitted to act in the presence of electric fields. I describe several simple problems that lead to effects that are not understood in any way, and I conclude with the proposition that what we know and believe are insignificant compared with the effects that we know to exist but cannot explain

Bringing firms on board. Inclusiveness of the dual apprenticeship systems in Germany, Switzerland and Denmark: Bringing firms on board

In dual vocational education and training (VET) systems, the state and employers collaborate in order to meet a country's needs in terms of education for youth and professional skills for the labour market. These systems are considered as effective tools to lower youth unemployment. However, since firms in dual VET systems select the apprentices, not every candidate gets access to in‐firm training. Consequently, governments develop measures that try to make their dual VET systems more inclusive. We present a categorisation of the different measures used to enhance inclusiveness in three dual collective skill formation countries (Switzerland, Germany and Denmark). We show that inclusiveness measures exist in each of the three countries but are limited in the extent to which firms are expected to play an active role in them. We conclude that the types of measures adopted are related to political economy traditions and the country's level of macro‐corporatism