The Perlick system type I: from the algebra of symmetries to the geometry of the trajectories

In this paper, we investigate the main algebraic properties of the maximally superintegrable system known as "Perlick system type I". All possible values of the relevant parameters, $K$ and $\beta$, are considered. In particular, depending on the sign of the parameter $K$ entering in the metrics, the motion will take place on compact or non compact Riemannian manifolds. To perform our analysis we follow a classical variant of the so called factorization method. Accordingly, we derive the full set of constants of motion and construct their Poisson algebra. As it is expected for maximally superintegrable systems, the algebraic structure will actually shed light also on the geometric features of the trajectories, that will be depicted for different values of the initial data and of the parameters. Especially, the crucial role played by the rational parameter $\beta$ will be seen "in action".Comment: 16 pages, 7 figure

Functions of innovation systems as a framework to understand sustainable technological change: empirical evidence for earlier claims

Understanding the emergence of innovation systems is recently put central in research analysing the process of technological change. Especially the key-activities that are important for the build up of an innovation system receive much attention. These are labeled ‘functions of innovation systems’. In most cases the authors apply this framework without questioning its validity. This paper builds on five empirical studies, related to renewable energy technologies, to test whether the functions of innovation systems framework is a valid framework to analyse processes of technological change. We test the claim that a specific set of functions is suitable. We also test whether the claim made in previous publications that the interactions between system functions accelerate innovation system emergence and growth is valid. Both claims are confirmed.

Anyons, group theory and planar physics

Relativistic and nonrelativistic anyons are described in a unified formalism by means of the coadjoint orbits of the symmetry groups in the free case as well as when there is an interaction with a constant electromagnetic field. To deal with interactions we introduce the extended Poincar\'e and Galilei Maxwell groups.Comment: 22 pages, journal reference added, bibliography update

Understanding innovation system build up: The rise and fall of the Dutch PV Innovation System

Renewable energy technologies have a hard time to break through in the existing energy regime. In this paper we focus on analysing the mechanisms behind this problematic technology diffusion. We take the theoretical perspective of innovation system dynamics and apply this to photovoltaic solar energy technology (PV) in the Netherlands. The reason for this is that there is a long history of policy efforts in The Netherlands to stimulate PV but results in terms of diffusion of PV panels is disappointingly low, which clearly constitutes a case of slow diffusion. The history of the development of the PV innovation system is analysed in terms of seven key processes that are essential for the build up of innovation systems. We show that the processes related to knowledge development are very stable but that large fluctuations are present in the processes related to ‘guidance of the search’ and ‘market formation’. Surprisingly, entrepreneurial activities are not too much affected by fluctuating market formation activities. We relate this to market formation in neighbouring countries and discuss the theoretical implications for the technological innovation system framework.Photovoltaic, Innovation system dynamics, Motors of Change

Refined Factorizations of Solvable Potentials

A generalization of the factorization technique is shown to be a powerful algebraic tool to discover further properties of a class of integrable systems in Quantum Mechanics. The method is applied in the study of radial oscillator, Morse and Coulomb potentials to obtain a wide set of raising and lowering operators, and to show clearly the connection that link these systems.Comment: 11 pages, LaTeX file, no figure

Comment on "Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin : The Tanger-Ketama Unit (external Rif, northern Morocco)" by Vázquez et al., Geologica Acta 11 (2013), 277-293

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Unpacking policy processes for addressing systemic problems in technological innovation systems: the case of offshore wind in Germany

While empirical studies on technological innovation systems (TIS) usually focus on policy instruments and their suitability for curing identified weaknesses of such emerging systems, the underlying policy processes and their effects have been largely disregarded. We address this gap by exploring the style of two crucial policy-making processes and how it influences the functioning and performance of a TIS, taking the case of offshore wind in Germany. Our findings indicate important positive and negative impacts of the policy style on the TIS. For example, the muddling through character apparent in one of the policy processes negatively influenced entrepreneurial activities, knowledge development and finally technology diffusion, whereas the participatory nature of both processes had a positive impact both on TIS functioning and performance. Based on our findings we derive implications on how to improve policy making so as to foster the development of an emerging TIS

High-density magnetomyography is superior to high-density surface electromyography for motor unit decomposition: a simulation study

Objective. Studying motor units is essential for understanding motor control, the detection of neuromuscular disorders and the control of human-machine interfaces. Individual motor unit firings are currently identified in vivo by decomposing electromyographic (EMG) signals. Due to our body’s properties and anatomy, individual motor units can only be separated to a limited extent with surface EMG. Unlike electrical signals, magnetic fields do not interact with human tissues. This physical property and the emerging technology of quantum sensors make magnetomyography (MMG) a highly promising methodology. However, the full potential of MMG to study neuromuscular physiology has not yet been explored. Approach. In this work, we perform in silico trials that combine a biophysical model of EMG and MMG with state-of-the-art algorithms for the decomposition of motor units. This allows the prediction of an upper-bound for the motor unit decomposition accuracy. Main results. It is shown that non-invasive high-density MMG data is superior over comparable high-density surface EMG data for the robust identification of the discharge patterns of individual motor units. Decomposing MMG instead of EMG increased the number of identifiable motor units by 76%. Notably, MMG exhibits a less pronounced bias to detect superficial motor units. Significance. The presented simulations provide insights into methods to study the neuromuscular system non-invasively and in vivo that would not be easily feasible by other means. Hence, this study provides guidance for the development of novel biomedical technologies

The irreducible unitary representations of the extended Poincare group in (1+1) dimensions

We prove that the extended Poincare group in (1+1) dimensions is non-nilpotent solvable exponential, and therefore that it belongs to type I. We determine its first and second cohomology groups in order to work out a classification of the two-dimensional relativistic elementary systems. Moreover, all irreducible unitary representations of the extended Poincare group are constructed by the orbit method. The most physically interesting class of irreducible representations corresponds to the anomaly-free relativistic particle in (1+1) dimensions, which cannot be fully quantized. However, we show that the corresponding coadjoint orbit of the extended Poincare group determines a covariant maximal polynomial quantization by unbounded operators, which is enough to ensure that the associated quantum dynamical problem can be consistently solved, thus providing a physical interpretation for this particular class of representations.Comment: 12 pages, Revtex 4, letter paper; Revised version of paper published in J. Math. Phys. 45, 1156 (2004