1,755 research outputs found
Die Ausbreitung von Währungskrisen
Währungskrisen einzelner Länder können weitreichende Folgen für die internationalen Devisen- und Finanzmärkte haben. Dafür gab es in den 90er Jahren viele Beispiele. Durch welche Transmissionskanäle breiteten sich diese Krisen aus? --
Band Gap and Edge Engineering via Ferroic Distortion and Anisotropic Strain: The Case of SrTiO
The effects of ferroic distortion and biaxial strain on the band gap and band
edges of SrTiO (STO) are calculated using density functional theory and
many-body perturbation theory. Anisotropic strains are shown to reduce the gap
by breaking degeneracies at the band edges. Ferroic distortions are shown to
widen the gap by allowing new band edge orbital mixings. Compressive biaxial
strains raise band edge energies, while tensile strains lower them. To reduce
the STO gap, one must lower the symmetry from cubic while suppressing ferroic
distortions. Our calculations indicate that for engineered orientation of the
growth direction along [111], the STO gap can be controllably and considerably
reduced at room temperature.Comment: 5 pages, 5 figures. To be published in Phys. Rev. Let
Banking union in Europe: How much centralisation is needed?
We examine the efficiency of banking regulation in a federation with two tiers of government and highly integrated banking systems. We assume that policy makers have incomplete information about banks’ true health, and banking sector turmoil can generate cross-border spill-over effects. We show that, in such an environment, the decentralisation of policy responsibilities for the regulation of banks can achieve the first-best allocation and ensure financial stability. While national governments design banking regulations, the federal policy maker authorises inter-regional income redistribution payments throughout the federation. Our results suggest that strengthening national responsibilities in banking regulation and supervision in the course of the further development of the European banking union may be advisable
Waste management regulation: Policy solutions and policy shortcomings
A model of packaging waste management is presented to explore the policy options available to governments to implement waste regulation in light of the Extended Producer Responsibility (EPR). Our model endogenises the packaging design as an additional determinant for the overall amount of waste jointly with consumers’ sorting effort and producers’ output decisions. The model shows that the policies that yield the first-best allocation may not find public support. Further, if the set of available policy instruments is limited, production and consumption of the good is likely to settle on a sub-optimal level even though the optimal allocation may be achievable. Finally, the model demonstrates that a landfill tax may actually increase landfill waste in the presence of tradable credits for recycling activities. The results shed light on some shortcomings of existing regulatory schemes such as the Producer Responsibility Obligations (Packaging Waste) Regulations of the UK
Anomalous frequency and intensity scaling of collective and local modes in a coupled spin tetrahedron system
We report on the magnetic excitation spectrum of the coupled spin tetrahedral
system CuTeOCl using Raman scattering on single
crystals. The transition to an ordered state at T=18.2 K evidenced
from thermodynamic data leads to the evolution of distinct low-energy magnetic
excitations superimposed by a broad maximum. These modes are ascribed to
magnons with different degree of localization and a two-magnon continuum. Two
of the modes develop a substantial energy shift with decreasing temperature
similar to the order parameter of other Neel ordered systems. The other two
modes show only a negligible temperature dependence and dissolve above the
ordering temperature in a continuum of excitations at finite energies. These
observations point to a delicate interplay of magnetic inter- and
intra-tetrahedra degrees of freedom and an importance of singlet fluctuations
in describing a spin dynamics.Comment: 7pages, 6figures, 1tabl
Gaussian matrix elements in a cylindrical harmonic oscillator basis
We derive a formalism, the separation method, for the efficient and accurate
calculation of two-body matrix elements for a Gaussian potential in the
cylindrical harmonic-oscillator basis. This formalism is of critical importance
for Hartree-Fock and Hartree-Fock-Bogoliubov calculations in deformed nuclei
using realistic, finite-range effective interactions between nucleons. The
results given here are also relevant for microscopic many-body calculations in
atomic and molecular physics, as the formalism can be applied to other types of
interactions beyond the Gaussian form. The derivation is presented in great
detail to emphasize the methodology, which relies on generating functions. The
resulting analytical expressions for the Gaussian matrix elements are checked
for speed and accuracy as a function of the number of oscillator shells and
against direct numerical integration.Comment: 55 pages, 9 figures, Computer Physics Communications 180, 1013-1040
(2009
Strongly hyperbolic Hamiltonian systems in numerical relativity: Formulation and symplectic integration
We consider two strongly hyperbolic Hamiltonian formulations of general
relativity and their numerical integration with a free and a partially
constrained symplectic integrator. In those formulations we use hyperbolic
drivers for the shift and in one case also for the densitized lapse. A system
where the densitized lapse is an external field allows to enforce the momentum
constraints in a holonomically constrained Hamiltonian system and to turn the
Hamilton constraint function from a weak to a strong invariant.
These schemes are tested in a perturbed Minkowski and the Schwarzschild
space-time. In those examples we find advantages of the strongly hyperbolic
formulations over the ADM system presented in [arXiv:0807.0734]. Furthermore we
observe stabilizing effects of the partially constrained evolution in
Schwarzschild space-time as long as the momentum constraints are enforced.Comment: This version clarifies some points concerning the interpretation of
the result
Retrieval of Biophysical Crop Variables from Multi-Angular Canopy Spectroscopy
The future German Environmental Mapping and Analysis Program (EnMAP) mission, due to launch in late 2019, will deliver high resolution hyperspectral data from space and will thus contribute to a better monitoring of the dynamic surface of the earth. Exploiting the satellite's +/- 30 degrees across-track pointing capabilities will allow for the collection of hyperspectral time-series of homogeneous quality. Various studies have shown the possibility to retrieve geo-biophysical plant variables, like leaf area index (LAI) or leaf chlorophyll content (LCC), from narrowband observations with fixed viewing geometry by inversion of radiative transfer models (RTM). In this study we assess the capability of the well-known PROSPECT 5B + 4SAIL (Scattering by Arbitrarily Inclined Leaves) RTM to estimate these variables from off-nadir observations obtained during a field campaign with respect to EnMAP-like sun-target-sensor-geometries. A novel approach for multiple inquiries of a large look-up-table (LUT) in hierarchical steps is introduced that accounts for the varying instances of all variables of interest. Results show that anisotropic effects are strongest for early growth stages of the winter wheat canopy which influences also the retrieval of the variables. RTM inversions from off-nadir spectra lead to a decreased accuracy for the retrieval of LAI with a relative root mean squared error (rRMSE) of 18% at nadir vs. 25% (backscatter) and 24% (forward scatter) at off-nadir. For LCC estimations, however, off-nadir observations yield improvements, i.e., rRMSE (nadir) = 24% vs. rRMSE (forward scatter) = 20%. It follows that for a variable retrieval through RTM inversion, the final user will benefit from EnMAP time-series for biophysical studies regardless of the acquisition angle and will thus be able to exploit the maximum revisit capability of the mission
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