Parasupersymmetric Quantum Mechanics with Generalized Deformed Parafermions

A superposition of bosons and generalized deformed parafermions corresponding to an arbitrary paraquantization order $p$ is considered to provide deformations of parasupersymmetric quantum mechanics. New families of parasupersymmetric Hamiltonians are constructed in connection with two examples of su(2) nonlinear deformations such as introduced by Polychronakos and Ro\v cek.Comment: 9 pages, LaTeX, no figures, to be published in Helv. Phys. Act

On oscillatorlike Hamiltonians and squeezing

Generalizing a recent proposal leading to one-parameter families of Hamiltonians and to new sets of squeezed states, we construct larger classes of physically admissible Hamiltonians permitting new developments in squeezing. Coherence is also discussed.Comment: 15 pages, Late

Parasupersymmetric Quantum Mechanics of Order 3 and a Generalized Witten Index

In this paper we generalize the Rubakov-Spiridonov parasupersymmetry algebra to the order 3 case. We also generalize the notion of the Witten index, and we provide a class of models satisfying our parasupersymmetry algebra. Finally, we show that there is a correspondence between the Hamiltonian and the index in our class of models

Dust particle(s) (as) diagnostics in plasmas

Complex plasmas are plasmas with dust particles or liquid droplets suspended in them. Under certain conditions dust particles spontaneously emerge in reactive plasmas. These plasmas, containing for instance fluorocarbon, hydrocarbon or silane molecules, are regularly named dusty plasmas. They have a broad range of applications in, for example, astrophysics (planetary rings, nebulae, comet tails, etc.). Also, the presence of dust particles in plasmas has considerable implications on plasma processes in the semiconductor and solar cell industry. Here, the properties of the plasma-processed surfaces can seriously be affected either negatively or positively; while contamination of semiconductor structures with dust particles might have a destructive effect, the incorporation of nanocrystals in deposited layers for solar cells can result in an increased efficiency and enhanced long-term stability of these devices. Another large application area is the presence of dust particles in fusion plasmas. In the plasma in these reactors, wall material can nucleate, forming dust particles that influence the plasma operation negatively. In all these applications, especially the dependence of dust particle formation on the gas temperature Tg is still not understood in full detail. In another field of research, dust particles (of several micrometers in size) are not created inside the plasma, but are injected from outside. These plasma configurations, often named complex plasmas, are regularly used for fundamental research. The highly negatively charged microparticles have the ability to form Coulomb crystals, making them representative macroscopic models for solid-state crystals and for phase transitions. Also, these charged particles can be confined within the space charge layer at the border of the discharge – the plasma sheath – where they can be used as electrostatic probes to measure the local electric field strength. In this thesis, two research lines are defined. In the first research line, we elaborate on the processes responsible for the formation and the growth of dust particles in low pressure hydrocarbon-containing (acetylene or methane) radiofrequency (RF) discharges. In acetylene, the first step in the dust particle formation process – the formation of negative ions – is studied by monitoring the time-evolution of both the electron density and the density of the first-formed and smallest negative ions (C2H- and/or H2CC-). Diagnostics used are microwave cavity resonance spectroscopy (MCRS) and laser-induced photodetachment. Both the formation and the destruction mechanisms of negative ions are found to be increasing functions of the gas temperature, the latter more so than the former. Since the rate of the dominant anion destruction channel (polymerization with neutral ground-state C2H2 precursor molecules) is independent of Tg, this is an indication for an increased density of (vibrationally) excited C2H??2 molecules at higher temperatures, enhancing polymerization rates. The coagulation onset time and the particle growth rate are studied in acetylene- and methane-containing discharges as function of the gas temperature as well. Used diagnostics are monitoring the time-evolution of the phase angle between the RF voltage and current, laser light scattering and, again, MCRS. In both gases, the coagulation onset time increases with decreasing pressure and increasing gas temperature. This behavior can be explained in terms of a changing gas density and a temperature dependent diffusion coefficient for nanoparticles. The growth rate of the dust particles decreases monotonically as function of Tg for methane containing discharges, and shows a maximum around Tg=65 0C for the acetylene case. A possible explanation for this behavior is a competition between increasing radical velocity towards the particle’s surface, decreasing radical sticking coefficients and decreasing particle densities, all at elevated temperatures. In the second research line, microparticles are injected into a collisional argon RF discharge and serve as electrostatic probes in the sheath region of the plasma. Probed parameters are the electric field strength and the particle charge, both obtained spatially resolved from measurements of the particle equilibrium position under varying apparent gravity conditions. Similar experiments are performed under hypergravity conditions (induced by a centrifuge) and under microgravity conditions (during parabolic flights). The results from the hypergravity experiments show a slightly non-linear electric field profile and indicate the presence of a maximum in the particle charge around 5.0 mm above the RF electrode. The microgravity experiments clearly show the transition region – the pre-sheath – separating the plasma sheath from the quasi-neutral plasma bulk, for instance by a kink in the electric field profile, and by dramatically changing ion and electron densities. Hence, we experimentally verify the existence of the pre-sheath region in RF discharges. From the measurements in concert with a simplified analytical sheath model, next to profiles for the electric field and the particle charge, profiles for the electron and ion density and for the directed ion velocity are obtained as well. The value of the directed velocity with which the ions enter the sheath region appears to be lower than the Bohm velocity, but still superthermal. Furthermore, from the experiments during the parabolic flights, interesting behavior is observed in terms of particle confinement in the absence of the apparent gravitational force. At pressures lower than ??0.2 mbar, the microparticles are lost from the discharge, while at higher pressures the particles remain confined within the sheath / pre-sheath. This behavior is explained by enhanced ion drag forces at higher pressures (increased ion density)

Local Molecular Dynamics with Coulombic Interaction

We propose a local, O(N) molecular dynamics algorithm for the simulation of charged systems. The long ranged Coulomb potential is generated by a propagating electric field that obeys modified Maxwell equations. On coupling the electrodynamic equations to an external thermostat we show that the algorithm produces an effective Coulomb potential between particles. On annealing the electrodynamic degrees of freedom the field configuration converges to a solution of the Poisson equation much like the electronic degrees of freedom approach the ground state in ab-initio molecular dynamics.Comment: 4 pages with 3 figure

“Untiring Labor Overcomes All!” The History of the Dutch Mathematical Society in Comparison to Its Various Counterparts in Europe

AbstractThe Netherlands, like some other European countries, witnessed the emergence of several amateur mathematical societies in a “philomathy” atmosphere during the 18th and early 19th century. One of them, the Amsterdam Mathematical Society “Untiring Labor Overcomes All” (nowadays known as the Wiskundig Genootschap), during the early 19th century became a national institution which embodied almost the entire Dutch mathematical community. It would fulfil its role as a national mathematical Society even before the 1860s, when pure mathematics became the subject of professional research and mathematical Societies of “professionals” were founded all over Europe. This article points out the Dutch social climate (the gap between the social classes was not as enormous as elsewhere in Europe, and engineering courses were part of the mathematics curriculum at the university) and changes within the Society itself, thus describing how it was possible for the Wiskundig Genootschap to become a link between two kinds of societies (“amateurs” vs “professionals”) which should be clearly distinguished. Copyright 2001 Academic Press.Zoals in vele Europese landen ontstonden er ook in Nederland gedurende de 18de en vroege 19de eeuw wiskundige genootschappen van “liefhebbers.” Een van deze amateurgezelschappen, het Amsterdams Wiskundig Genootschap onder de zinspreuk “onvermoeide arbeid komt alles te boven,” groeide gedurende de eerste decennia van de 19de eeuw uit tot een nationaal genootschap dat de Nederlandse wiskundige gemeenschap vertegenwoordigde. Het genootschap vervulde haar rol van nationaal genootschap zodoende reeds lang voordat in de jaren 1860 onder invloed van professionalisering van (wiskundig) onderzoek dergelijke genootschappen van “professionals” in de andere Europese landen opkwamen. In dit artikel wordt gewezen op het sociale klimaat (er was nauwelijks sprake van een kloof tussen de sociale klassen zoals elders in Europa, en ingenieurswiskunde maakte deel uit van het universitair curriculum) en veranderingen binnen het genootschap zelf, waarmee beschreven wordt hoe het Wiskundig Genootschap een verband vormt tussen twee soorten van genootschappen (“amateurs” vs “professionals”) die nadrukkelijk van elkaar onderscheiden dienen te worden. Copyright 2001 Academic Press.MSC 1991 subject classifications: 01A50, 01A55

Corporate real estate strategies for future higher education

Purpose – This paper aims to explore the alignment of Corporate Real Estate (CRE) strategies of Dutch Universities of Applied Sciences (UAS) with the developments in higher education

Surprising temperature dependence of the dust particle growth rate in low pressure Ar/C2H2 plasmas

We have experimentally monitored the growth rate of dust particles in a low pressure Ar/C2H2 radiofrequency discharge as a function of the gas temperature Tg and independent of the C2H radical density and the gas density. Used diagnostics are laser light scattering and measurements of the phase angle between the RF voltage and current. In contrast to most literature, we demonstrate that the growth rate is not a monotonically decreasing function of Tg but shows a maximum around Tg¿=¿65¿°C. In addition, we demonstrate that the phase angle is an accurate measure to monitor the particle growth rat