2,030 research outputs found
Three-dimensional U(1) gauge+Higgs theory as an effective theory for finite temperature phase transitions
We study the three-dimensional U(1)+Higgs theory (Ginzburg-Landau model) as
an effective theory for finite temperature phase transitions from the 1 K scale
of superconductivity to the relativistic scales of scalar electrodynamics. The
relations between the parameters of the physical theory and the parameters of
the 3d effective theory are given. The 3d theory as such is studied with
lattice Monte Carlo techniques. The phase diagram, the characteristics of the
transition in the first order regime, and scalar and vector correlation lengths
are determined. We find that even rather deep in the first order regime, the
transition is weaker than indicated by 2-loop perturbation theory. Topological
effects caused by the compact formulation are studied, and it is demonstrated
that they vanish in the continuum limit. In particular, the photon mass
(inverse correlation length) is observed to be zero within statistical errors
in the symmetric phase, thus constituting an effective order parameter.Comment: 42 pages, 14 figure
Vortices in equilibrium scalar electrodynamics
Scalar electrodynamics can be used to investigate the formation of cosmic
strings in the early universe. We present the results of lattice Monte Carlo
simulations of an effective three-dimensional U(1)+Higgs theory that describes
the equilibrium properties of finite-temperature scalar electrodynamics near
the transition. A gauge-invariant criterion for the existence of a vortex is
used in measuring the properties of the vortex network in the equilibrium state
both in the Coulomb and in the Higgs phase of the system. The naive definition
of the vortex density becomes meaningless in the continuum limit and special
care is needed in extracting physical quantities. Numerical evidence for a
physical discontinuity in the vortex density is given.Comment: 4 pages. Talk given by A. Rajantie at PASCOS-98, March 199
Feasibility of Active Ingredient (AI) development for new biocides in the EU
Biocides usage covers a vast industrial area and the history of biocide and other antimicrobial agent usage in various forms and applications dates back centuries. While the emerging EU regulations (BPD, REACH and others) strive to increase the safety and the eco-efficiency of chemical products and production processes, such changes may also create voids in the availability of current biocides due to outphasing. The present study evaluated the need for new Active Ingredient (AI) development. The feasibility of such development was explored, and the data of economic feasibility analysis shows that, contrary to general expectations, AI development can become profitable within certain economic boundaries
Masses and Phase Structure in the Ginzburg-Landau Model
We study numerically the phase structure of the Ginzburg-Landau model, with
particular emphasis on mass measurements. There is no local gauge invariant
order parameter, but we find that there is a phase transition characterized by
a vanishing photon mass. For type I superconductors the transition is of 1st
order. For type II 1st order is excluded by susceptibility analysis, but the
photon correlation length suggests 2nd order critical behaviour with \nu ~ 1/2.
The scalar mass, in contrast, does not show clear critical behaviour in the
type II regime for V \to \infty, contrary to the conventional picture.Comment: 16 pages, 6 figures. More data gathered, allowing more definite
conclusion
Forest inventory attribute estimation using airborne laser scanning, aerial stereoimagery, radargrammetry and interferometry - Finnish experiences of the 3D techniques
Three-dimensional (3D) remote sensing has enabled detailed mapping of terrain and vegetation heights. Consequently, forest
inventory attributes are estimated more and more using point clouds and normalized surface models. In practical applications,
mainly airborne laser scanning (ALS) has been used in forest resource mapping. The current status is that ALS-based forest
inventories are widespread, and the popularity of ALS has also raised interest toward alternative 3D techniques, including airborne
and spaceborne techniques. Point clouds can be generated using photogrammetry, radargrammetry and interferometry. Airborne
stereo imagery can be used in deriving photogrammetric point clouds, as very-high-resolution synthetic aperture radar (SAR) data
are used in radargrammetry and interferometry. ALS is capable of mapping both the terrain and tree heights in mixed forest
conditions, which is an advantage over aerial images or SAR data. However, in many jurisdictions, a detailed ALS-based digital
terrain model is already available, and that enables linking photogrammetric or SAR-derived heights to heights above the ground.
In other words, in forest conditions, the height of single trees, height of the canopy and/or density of the canopy can be measured
and used in estimation of forest inventory attributes. In this paper, first we review experiences of the use of digital stereo imagery
and spaceborne SAR in estimation of forest inventory attributes in Finland, and we compare techniques to ALS. In addition, we
aim to present new implications based on our experiences
Extracting Urban Morphology for Atmospheric Modeling from Multispectral and SAR Satellite Imagery
This paper presents an approach designed to derive an urban morphology map from satellite data while aiming to minimize the cost of data and user interference. The approach will help to provide updates to the current morphological databases around the world. The proposed urban morphology maps consist of two layers: 1) Digital Elevation Model (DEM) and 2) land cover map. Sentinel-2 data was used to create a land cover map, which was realized through image classification using optical range indices calculated from image data. For the purpose of atmospheric modeling, the most important classes are water and vegetation areas. The rest of the area includes bare soil and built-up areas among others, and they were merged into one class in the end. The classification result was validated with ground truth data collected both from field measurements and aerial imagery. The overall classification accuracy for the three classes is 91 %. TanDEM-X data was processed into two DEMs with different grid sizes using interferometric SAR processing. The resulting DEM has a RMSE of 3.2 meters compared to a high resolution DEM, which was estimated through 20 control points in flat areas. Comparing the derived DEM with the ground truth DEM from airborne LIDAR data, it can be seen that the street canyons, that are of high importance for urban atmospheric modeling are not detectable in the TanDEM-X DEM. However, the derived DEM is suitable for a class of urban atmospheric models. Based on the numerical modeling needs for regional atmospheric pollutant dispersion studies, the generated files enable the extraction of relevant parametrizations, such as Urban Canopy Parameters (UCP).Peer reviewe
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