Collectivity, Phase Transitions and Exceptional Points in Open Quantum Systems

Phase transitions in open quantum systems, which are associated with the formation of collective states of a large width and of trapped states with rather small widths, are related to exceptional points of the Hamiltonian. Exceptional points are the singularities of the spectrum and eigenfunctions, when they are considered as functions of a coupling parameter. In the present paper this parameter is the coupling strength to the continuum. It is shown that the positions of the exceptional points (their accumulation point in the thermodynamical limit) depend on the particular type and energy dependence of the coupling to the continuum in the same way as the transition point of the corresponding phase transition.Comment: 22 pages, 4 figure

Using straw in steep furrows to reduce soil erosion and increase dry bean yields

Furrow-irrigated fields often have different slopes along a furrow, which tend to cause different water intakes and erosion rates. Irrigated furrows on the steeper slopes develop narrow channels that reduce the wetted perimeter in the furrow. This results in lower infiltration, and crops growing on the steep acres do not receive adequate water for the highest crop yield. Plants growing adjacent to straw-treated furrows received 1.3 to 2.1 times as much irrigation water as plants growing next to untreated furrows. Dry bean yield increases on the straw-treated furrows, compared to the untreated furrows, ranged from 614 kg/ha to 1,306 kg/ha—a 21 % to 62 % increase, respectively. Also, sediment yield reductions in the straw-treated furrows ranged from 69% to 90 % compared to untreated furrows

Overture: An advanced object-oriented software system for moving overlapping grid computations

While the development of high-level, easy-to-use, software libraries for numerical computations has been successful in some areas (e.g. linear system solvers, ODE solvers, grid generation), this has been an elusive goal for developers of partial differential equation (PDE) solvers. The advent of new high level languages such as C++ has begun to make this an achievable goal. This report discusses an object- oriented environment that we are developing for solving problems on overlapping (Chimera) grids. The goal of this effort is to support flexible PDE solvers on adaptive, moving, overlapping grids that cover a domain and overlap where they meet. Solutions values at the overlap are determined by interpolation. The overlapping grid approach is particularly efficient for rapidly generating high- quality grids for moving geometries since as the component grids move, only the list of interpolation points changes, and the component grids do not have to be regenerated. We use structured component grids so that efficient, fast finite-difference algorithms can be used. Oliger-Berger-Corella type mesh refinement is used to efficiently resolve fine features of the flow

Surface Tension between Kaon Condensate and Normal Nuclear Matter Phase

We calculate for the first time the surface tension and curvature coefficient of a first order phase transition between two possible phases of cold nuclear matter, a normal nuclear matter phase in equilibrium with a kaon condensed phase, at densities a few times the saturation density. We find the surface tension is proportional to the difference in energy density between the two phases squared. Furthermore, we show the consequences for the geometrical structures of the mixed phase region in a neutron star.Comment: 7 pages, 5 figures (Latex

Ultrafine particle deposition and clearance in the healthy and obstructed lung

Numerous epidemiologic studies have shown associations between exposure to particulate air pollution and acute increases in morbidity and mortality, particularly in persons with chronic obstructive pulmonary disease. The dosimetry of ultrafine particles in the human lung is poorly characterized. We studied the deposition and clearance of an ultrafine technetium-99m-labeled aerosol in 10 patients with chronic obstructive pulmonary disease and in 9 healthy subjects. Particle retention was followed for 2 hours after inhalation and again at 24 hours by γ scintigraphy. Central-to-peripheral ratios indexed airway deposition. Particle accumulation in the liver was examined by quantifying activity below the right lung. The dose rate for an aerosol exposure of 10 μg/m3 was calculated. Patients had a significantly greater dose rate than healthy subjects (2.9 ± 1.0 versus 1.9 ± 0.4 μg/h, p = 0.02). Central-to-peripheral ratios were slightly greater in patients than in healthy subjects (1.11 ± 0.10 versus 1.01 ± 0.11, p = 0.05). Clearance did not statistically differ between health and disease. On average, 24-hour retention was 85 ± 8% (corrected for isotope dissolution). No accumulation in the liver's vicinity was observed. Data suggest that relative to healthy subjects, patients with moderate-to-severe airways obstruction receive an increased dose from ultrafine particle exposure

Positive Self-Adjoint Operator Extensions with Applications to Differential Operators

In this paper we consider extensions of positive operators. We study the connections between the von Neumann theory of extensions and characterisations of positive extensions via decompositions of the domain of the associated form. We apply the results to elliptic second-order differential operators and look in particular at examples of the Laplacian on a disc and the Aharanov-Bohm operator

Is classical reality completely deterministic?

The concept of determinism for a classical system is interpreted as the requirement that the solution to the Cauchy problem for the equations of motion governing this system be unique. This requirement is generally assumed to hold for all autonomous classical systems. We give counterexamples of this view. Our analysis of classical electrodynamics in a world with one temporal and one spatial dimension shows that the solution to the Cauchy problem with the initial conditions of a particular type is not unique. Therefore, random behavior of closed classical systems is indeed possible. This finding provides a qualitative explanation of how classical strings can split. We propose a modified path integral formulation of classical mechanics to include indeterministic systems.Comment: Replace the paper with a revised versio

Sediment, erosion and water intake in furrows

Observations and studies were conducted on the origin and destination of sediment in irrigation water, and the effects of sediment adsorbed on the wetted perimeter of furrows on water intake and erosion. Fine sediment adsorbed on the perimeter reduced intake and increased soil water tension which was the primary mechanism holding the sediment on the perimeter. This self enhancing effect causes this thin seal to decrease erosion and intake rates. In contrast, removal of a few square centimeters of this seal by chance events after water velocities and shear forces have increased often causes reduced tensions, exfoliation of the surface seal and erosion pits which develop into head cuts

Overture: an object-oriented software system for solving partial differential equations in serial and parallel environments

The OVERTURE Framework is an object-oriented environment for solving PDEs on serial and parallel architectures. It is a collection of C++ libraries that enables the use of finite difference and finite volume methods at a level that hides the details of the associated data structures, as well as the details of the parallel implementation. It is based on the A++/P++ array class library and is designed for solving problems on a structured grid or a collection of structured grids. In particular, it can use curvilinear grids, adaptive mesh refinement and the composite overlapping grid method to represent problems with complex moving geometry

Crop Residue Management for Soil Conservation on Irrigated Lands of the Northwest

Leaving crop residue on the soil surface during cropping has a number of clear advantages over tillage that leaves the soil surface bare. Most obvious is the greatly reduced erosion from wind and water. This advantage alone makes the change worthwhile. Mandated conservation compliance by 1995 is a further incentive to adopt surface crop residue management. Other advantages include increased yield due to water conserved by surface residue, lower soil temperatures, higher quality soil over time due to increased soil organic matter levels, and, in many cases, reduced input of time, labor, and fuel. The feasibility of farming while leaving residues on the surface is indicated by the rapid rate at which farmers are adopting these management practices. Success is due in large part to greater effectiveness and reduced cost of herbicides and the improvement of planting equipment available on the market