Do We Understand Quantum Mechanics - Finally?

After some historical remarks concerning Schroedinger's discovery of wave mechanics, we present a unified formalism for the mathematical description of classical and quantum-mechanical systems, utilizing elements of the theory of operator algebras. We then review some basic aspects of quantum mechanics and, in particular, of its interpretation. We attempt to clarify what Quantum Mechanics tells us about Nature when appropriate experiments are made. We discuss the importance of the mechanisms of "dephasing" and "decoherence" in associating "facts" with possible events and rendering complementary possible events mutually exclusive.Comment: 42 pages, contribution to the Proceedings of a conference in memory of Erwin Schroedinger, Vienna, January 201

Basic Types of Coarse-Graining

We consider two basic types of coarse-graining: the Ehrenfests' coarse-graining and its extension to a general principle of non-equilibrium thermodynamics, and the coarse-graining based on uncertainty of dynamical models and Epsilon-motions (orbits). Non-technical discussion of basic notions and main coarse-graining theorems are presented: the theorem about entropy overproduction for the Ehrenfests' coarse-graining and its generalizations, both for conservative and for dissipative systems, and the theorems about stable properties and the Smale order for Epsilon-motions of general dynamical systems including structurally unstable systems. Computational kinetic models of macroscopic dynamics are considered. We construct a theoretical basis for these kinetic models using generalizations of the Ehrenfests' coarse-graining. General theory of reversible regularization and filtering semigroups in kinetics is presented, both for linear and non-linear filters. We obtain explicit expressions and entropic stability conditions for filtered equations. A brief discussion of coarse-graining by rounding and by small noise is also presented.Comment: 60 pgs, 11 figs., includes new analysis of coarse-graining by filtering. A talk given at the research workshop: "Model Reduction and Coarse-Graining Approaches for Multiscale Phenomena," University of Leicester, UK, August 24-26, 200

The kinetics of ice-lens growth in porous media

We analyse the growth rate of segregated ice (ice lenses) in freezing porous media. For typical colloidal materials such as soils we show that the commonly-employed Clapeyron equation is not valid macroscopically at the interface between the ice lens and the surrounding porous medium owing to the viscous dynamics of flow in premelted films. This gives rise to an ‘interfacial resistance’ to flow towards the growing ice which causes a significant drop in predicted ice-growth (heave) rates and explains why many previous models predict ice-growth rates that are much larger than those seen in experiments. We derive an explicit formula for the ice-growth rate in a given porous medium, and show that this only depends on temperature and on the external pressures imposed on the freezing system. This growth-rate formula contains a material-specific function which can be calculated (with a knowledge of the of the geometry and material of the porous medium), but which is also readily experimentally-measurable. We apply the formula to plate-like particles, and obtain good agreement with previous experimental data. Finally we show how the interfacial resistance explains the observation that the maximum heave rate in soils occurs in medium-grained particles such as silts, while heave rates are smaller for fine- and coarse- grained particles

The radiation field in the Gamma Irradiation Facility GIF++ at CERN

The high-luminosity LHC (HL-LHC) upgrade is setting now a new challenge for particle detector technologies. The increase in luminosity will produce a particle background in the gas-based muon detectors that is ten times higher than under conditions at the LHC. The detailed knowledge of the detector performance in the presence of such a high background is crucial for an optimized design and efficient operation after the HL-LHC upgrade. A precise understanding of possible aging effects of detector materials and gases is of extreme importance. To cope with these challenging requirements, a new Gamma Irradiation Facility (GIF++) was designed and built at the CERN SPS North Area as successor of the Gamma Irradiation Facility (GIF) during the Long Shutdown 1 (LS1) period. It features an intense source of 662 keV photons with adjustable intensity, to simulate continuous background over large areas, and, combined with a high energy muon beam, to measure detector performance in the presence of the background. The new GIF++ facility has been operational since spring 2015. In addition to describing the facility and its infrastructure, the goal of this work is to provide an extensive characterization of the GIF++ photon field with different configurations of the absorption filters in both the upstream and downstream irradiation areas. Moreover, the measured results are benchmarked with Geant4 simulations to enhance the knowledge of the radiation field. The absorbed dose in air in the facility may reach up to 2.2 Gy/h directly in front of the irradiator. Of special interest is the low-energy photon component that develops due to the multiple scattering of photons within the irradiator and from the concrete walls of the bunker

Formation control of nonholonomic mobile robots using implicit polynomials and elliptic Fourier descriptors

This paper presents a novel method for the formation control of a group of nonholonomic mobile robots using implicit and parametric descriptions of the desired formation shape. The formation control strategy employs implicit polynomial (IP) representations to generate potential fields for achieving the desired formation and the elliptical Fourier descriptors (EFD) to maintain the formation once achieved. Coordination of the robots is modeled by linear springs between each robot and its two nearest neighbors. Advantages of this new method are increased flexibility in the formation shape, scalability to different swarm sizes and easy implementation. The shape formation control is first developed for point particle robots and then extended to nonholonomic mobile robots. Several simulations with robot groups of different sizes are presented to validate our proposed approach