Ideal Bose gas in fractal dimensions and superfluid 4^4He in porous media

Physical properties of ideal Bose gas with the fractal dimensionality between D=2 and D=3 are theoretically investigated. Calculation shows that the characteristic features of the specific heat and the superfluid density of ideal Bose gas in fractal dimensions are strikingly similar to those of superfluid Helium-4 in porous media. This result indicates that the geometrical factor is dominant over mutual interactions in determining physical properties of Helium-4 in porous media.Comment: 13 pages, 6 figure

The Potential for Electromagnetic Metal Forming for Plane (Car Body) Components

Classical quasi-static technologies of sheet metal forming are not the only domain of the Fraunhofer Institute for Machine Tools and Forming Technology (IWU). It also delves into techniques for high-energy rate forming, such as gas generator technology, and it will be dedicating greater efforts to electromagnetic metal forming. Electromagnetic metal forming processes major potential for innovation and development in manufacturing car-body components since the benefits to be derived from this technique (such as extending the limitations of forming, enhancing spring back behavior, and delivering a high degree of flexibility in production) have this sector's key problems in mind. The Fraunhofer Institute for Machine Tools and Forming Technology focuses its research on coming up with technology, tool and plant strategies suitable for manufacturing medium-sized and large car-body components. There are two technological directions that IWU targets in this field of research. First of all, given the existing technical and physical process constraints, it is studying the possibilities of large-scale and partial deformation since both directions are of importance for the targeted products. However, these two approaches have very different requirements for designing and tools. The first approach forms components without preforming. Several forming steps are required for mapping typical car-body component shapes either with serial workstations or a flexible tool system. The partial electromagnetic metal forming approach means using integrated plant components, i.e. combining conventional press equipment with a magnetic forming plant. This can tap a potential that encompasses the technological benefits mentioned above while hiking productivity and scaling down the expenditures for investing in equipment

Error analysis of ICESat waveform processing by investigating overlapping pairs over Europe

Full waveform laser altimetry is a recently developed method to obtain a complete vertical profile of the height of objects in the footprint as illuminated by a laser pulse. The richness of the signal also complicates the processing. One way to improve the processing strategy is to analyze differences of waveforms that should be very similar because they were obtained at approximately the same time and location. Such waveform pairs are still difficult to find. Here it is shown how to use the archive of ICESat space-borne altimetry data over Europe to determine a set of tenths of thousands of at least partial overlapping waveform pairs. The differences in the values of the waveform parameters, median energy, waveform extent, relative returned energy and intensity distribution are determined and discussed. As a case study, three typical pairs of almost perfectly overlapping waveforms are shown, were considerable differences are still occurring. In all three cases an explanation for these differences is found and discussed. Further analysis of the waveform pairs in this database is expected to considerably improve automatic processing of full waveform data

Coherent control for the spherical symmetric box potential in short and intensive XUV laser fields

Coherent control calculations are presented for a spherically symmetric box potential for non-resonant two photon transition probabilities. With the help of a genetic algorithm (GA) the population of the excited states are maximized and minimized. The external driving field is a superposition of three intensive extreme ultraviolet (XUV) linearly polarized laser pulses with different frequencies in the femtosecond duration range. We solved the quantum mechanical problem within the dipole approximation. Our investigation clearly shows that the dynamics of the electron current has a strong correlation with the optimized and neutralizing pulse shape.Comment: 11 Pages 3 Figure

First order wetting of rough substrates and quantum unbinding

Replica and functional renormalization group methods show that, with short range substrate forces or in strong fluctuation regimes, wetting of a self-affine rough wall in 2D turns first-order as soon as the wall roughness exponent exceeds the anisotropy index of bulk interface fluctuations. Different thresholds apply with long range forces in mean field regimes. For bond-disordered bulk, fixed point stability suggests similar results, which ultimately rely on basic properties of quantum bound states with asymptotically power-law repulsive potentials.Comment: 11 pages, 1 figur

Correlation length by measuring empty space in simulated aggregates

We examine the geometry of the spaces between particles in diffusion-limited cluster aggregation, a numerical model of aggregating suspensions. Computing the distribution of distances from each point to the nearest particle, we show that it has a scaled form independent of the concentration phi, for both two- (2D) and three-dimensional (3D) model gels at low phi. The mean remoteness is proportional to the density-density correlation length of the gel, xi, allowing a more precise measurement of xi than by other methods. A simple analytical form for the scaled remoteness distribution is developed, highlighting the geometrical information content of the data. We show that the second moment of the distribution gives a useful estimate of the permeability of porous media.Comment: 4 page

Tectonics of the Lepontine Alps: ductile thrusting and folding in the deepest tectonic levels of the Central Alps

The Lepontine dome represents a unique region in the arc of the Central and Western Alps, where complex fold structures of upper amphibolite facies grade of the deepest stage of the orogenic belt are exposed in a tectonic half-window. The NW-verging Mont Blanc, Aar und Gotthard basement folds and the Lower Penninic gneiss nappes of the Central Alps were formed by ductile detachment of the upper European crust during its Late Eocene–Early Oligocene SE-directed underthrust below the upper Penninic and Austroalpine thrusts and the Adriatic plate. Four underthrust zones are distinguished in the NW-verging stack of Alpine fold nappes and thrusts: the Canavese, Piemont, Valais and Adula zones. Up to three schistosities S1–S3, folds F1–F3 and a stretching lineation XI with top-to-NW shear indicators were developed in the F1–F3 fold nappes. Spectacular F4 transverse folds, the SW-verging Verzasca, Maggia, Ziccher, Alpe Bosa and Wandfluhhorn anticlines and synclines overprint the Alpine nappe stack. Their formation under amphibolite facies grade was related to late ductile folding of the southern nappe roots during dextral displacement of the Adriatic indenter. The transverse folding F4 was followed since 30 Ma by the pull-apart exhumation and erosion of the Lepontine dome. This occurred coevally with the formation of the dextral ductile Simplon shear zone, the S-verging backfolding F5 and the formation of the southern steep belt. Exhumation continued after 18 Ma with movement on the brittle Rhone-Simplon detachment, accompanied by the N-, NW- and W-directed Helvetic and Dauphiné thrusts. The dextral shear is dated by the 29–25 Ma crustal-derived aplite and pegmatite intrusions in the southern steep belt. The cooling by uplift and erosion of the Tertiary migmatites of the Bellinzona region occurred between 22 and 18 Ma followed by the exhumation of the Toce dome on the brittle Rhone–Simplon fault since 18 Ma

Limitations on the superposition principle: superselection rules in non-relativistic quantum mechanics

The superposition principle is a very basic ingredient of quantum theory. What may come as a surprise to many students, and even to many practitioners of the quantum craft, is tha superposition has limitations imposed by certain requirements of the theory. The discussion of such limitations arising from the so-called superselection rules is the main purpose of this paper. Some of their principal consequences are also discussed. The univalence, mass and particle number superselection rules of non-relativistic quantum mechanics are also derived using rather simple methods.Comment: 22 pages, no figure

A Theory of Cheap Control in Embodied Systems

We present a framework for designing cheap control architectures for embodied agents. Our derivation is guided by the classical problem of universal approximation, whereby we explore the possibility of exploiting the agent's embodiment for a new and more efficient universal approximation of behaviors generated by sensorimotor control. This embodied universal approximation is compared with the classical non-embodied universal approximation. To exemplify our approach, we present a detailed quantitative case study for policy models defined in terms of conditional restricted Boltzmann machines. In contrast to non-embodied universal approximation, which requires an exponential number of parameters, in the embodied setting we are able to generate all possible behaviors with a drastically smaller model, thus obtaining cheap universal approximation. We test and corroborate the theory experimentally with a six-legged walking machine. The experiments show that the sufficient controller complexity predicted by our theory is tight, which means that the theory has direct practical implications. Keywords: cheap design, embodiment, sensorimotor loop, universal approximation, conditional restricted Boltzmann machineComment: 27 pages, 10 figure