1,957 research outputs found
On the robustness of concealing cost information in oligopoly
Competing firms are usually better informed about their own cost parameters than about those of their rivals. Therefore, it is an important issue to study the incentives of firms to exchange private cost information. We resolve and further generalize an influential model of Raith (1996) and show that, independent of the number of firms, concealing cost information is a dominant firm strategy in heterogeneous Bertrand oligopolies with substitutive as well as with complementary goods.cost uncertainty
No information sharing in oligopoly : the case of price competition with cost uncertainty
We show that concealing cost information is a dominant strategy in heterogeneous
Bertrand oligopolies. This result enables us to endogenize the number of firms in a
market in terms of market size, entry costs, and unit cost uncertainty.In diesem Beitrag zeigen wir, daĂź fĂĽr ein heterogenes Oligopol die dominante Strategie
der Unternehmen bei Preiswettbewerb lautet, keine Informationen ĂĽber die
Höhe der Produktionsstückkosten auszutauschen. Auf der Basis dieses Ergebnisses
läßt sich die Anzahl der Unternehmen im Markt in Abhängigkeit vom Marktvolumen,
von den Kosten des Marktzutritts und von der Unsicherheit über die Höhe
der ProduktionsstĂĽckkosten endogenisieren
Electrode effects on the observability of destructive quantum interference in single-molecule junctions
Destructive quantum interference (QI) has been a source of interest as a new
paradigm for molecular electronics as the electronic conductance is widely
dependent on the occurrence or absence of destructive QI effects. In order to
interpret experimentally observed transmission features, it is necessary to
understand the effects of all components of the junction on electron transport.
We perform non-equilibrium Green's function calculations within the framework
of density functional theory to assess the structure-function relationship of
transport through pyrene molecular junctions with distinct QI properties. The
chemical nature of the anchor groups and the electrodes controls the Fermi
level alignment, which determines the observability of destructive QI. A
thorough analysis allows to disentangle the transmission features arising from
the molecule and the electrodes. Interestingly, graphene electrodes introduce
features in the low-bias regime, which can either mask or be misinterpreted as
QI effects, while instead originating from the topological properties of the
edges. Thus, this first principles analysis provides clear indications to guide
the interpretation of experimental studies, which cannot be obtained from
simple H\"uckel model calculations.Comment: 12 pages, 8 figure
Wettbewerb bei unvollständiger Information: Informationsaustausch oder stillschweigende Kollusion?
Der Beitrag sollte verdeutlichen, dass sich seit den Pioniermodellen mit unvollständiger Information mittlerweile eine recht heterogene Klasse von Ansätzen etabliert hat, die sich unter alternativen Grundannahmen mit der Frage auseinandersetzen, ob Unternehmen angesichts diverser Unsicherheiten auf ihren Märkten einen Anreiz besitzen, ihre privaten Informationen mit Konkurrenten zu teilen (Informationsaustausch) oder diese für sich zu behalten (stillschweigende Kollusion). Auf der Basis der bestehenden Literatur demonstrierte der vorliegende Beitrag ausgehend von einem Referenzmodell mit vollständiger Information die einfachst mögliche Modellierung unvollständiger Kosten- und Nachfrageinformation, mit der sich die Frage des Informationsaustausches zwischen Unternehmen in oligopolistischen Marktstrukturen modelltheoretisch erfassen lässt. Er liefert eine einleuchtende Erklärung für das immer wieder festzustellende Phänomen, dass die Unternehmen einer Branche zwar ihre jeweiligen Informationen über die Nachfragesituation bereitwillig den Konkurrenten zur Verfügung stellen, jedoch keinerlei Informationen über die verwendete Produktionstechnologie preisgeben. Die optimale Informationspolitik eines erfolgreichen Unternehmens obliegt folglich der Kunst zu wissen, worüber man spricht und worüber man besser schweigt
Landscape statistics of the low autocorrelated binary string problem
The statistical properties of the energy landscape of the low autocorrelated
binary string problem (LABSP) are studied numerically and compared with those
of several classic disordered models. Using two global measures of landscape
structure which have been introduced in the Simulated Annealing literature,
namely, depth and difficulty, we find that the landscape of LABSP, except
perhaps for a very large degeneracy of the local minima energies, is
qualitatively similar to some well-known landscapes such as that of the
mean-field 2-spin glass model. Furthermore, we consider a mean-field
approximation to the pure model proposed by Bouchaud and Mezard (1994, J.
Physique I France 4 1109) and show both analytically and numerically that it
describes extremely well the statistical properties of LABSP
SuperConga: an open-source framework for mesoscopic superconductivity
We present SuperConga, an open-source framework for simulating equilibrium
properties of unconventional and ballistic singlet superconductors, confined to
two-dimensional (2D) mesoscopic grains in a perpendicular external magnetic
field, at arbitrary low temperature. It aims at being both fast and easy to
use, enabling research without access to a computer cluster, and visualization
in real-time with OpenGL. The core is written in C++ and CUDA, exploiting the
embarrassingly parallel nature of the quasiclassical theory of
superconductivity by utilizing the parallel computational power of modern GPUs.
The framework self-consistently computes both the superconducting
order-parameter and the induced vector potential, and finds the current
density, free energy, induced flux density, local density of states, as well as
the magnetic moment. A user-friendly Python frontend is provided, enabling
simulation parameters to be defined via intuitive configuration files, or via
the command-line interface, without requiring a deep understanding of
implementation details. For example, complicated geometries can be created with
relative ease. The framework ships with simple tools for analyzing and
visualizing the results, including an interactive plotter for spectroscopy. An
overview of the theory is presented, as well as examples showcasing the
framework's capabilities and ease of use. The framework is free to download
from https://gitlab.com/superconga/superconga, which also links to the
extensive user manual, containing even more examples, tutorials and guides.Comment: Accepted version. Review-style article, 31 pages and link to software
at https://gitlab.com/superconga/supercong
First experimental results of very high accuracy centroiding measurements for the neat astrometric mission
NEAT is an astrometric mission proposed to ESA with the objectives of
detecting Earth-like exoplanets in the habitable zone of nearby solar-type
stars. NEAT requires the capability to measure stellar centroids at the
precision of 5e-6 pixel. Current state-of-the-art methods for centroid
estimation have reached a precision of about 2e-5 pixel at two times Nyquist
sampling, this was shown at the JPL by the VESTA experiment. A metrology system
was used to calibrate intra and inter pixel quantum efficiency variations in
order to correct pixelation errors. The European part of the NEAT consortium is
building a testbed in vacuum in order to achieve 5e-6 pixel precision for the
centroid estimation. The goal is to provide a proof of concept for the
precision requirement of the NEAT spacecraft. In this paper we present the
metrology and the pseudo stellar sources sub-systems, we present a performance
model and an error budget of the experiment and we report the present status of
the demonstration. Finally we also present our first results: the experiment
had its first light in July 2013 and a first set of data was taken in air. The
analysis of this first set of data showed that we can already measure the pixel
positions with an accuracy of about 1e-4 pixel.Comment: SPIE conference proceeding
A detector interferometric calibration experiment for high precision astrometry
Context: Exoplanet science has made staggering progress in the last two
decades, due to the relentless exploration of new detection methods and
refinement of existing ones. Yet astrometry offers a unique and untapped
potential of discovery of habitable-zone low-mass planets around all the
solar-like stars of the solar neighborhood. To fulfill this goal, astrometry
must be paired with high precision calibration of the detector.
Aims: We present a way to calibrate a detector for high accuracy astrometry.
An experimental testbed combining an astrometric simulator and an
interferometric calibration system is used to validate both the hardware needed
for the calibration and the signal processing methods. The objective is an
accuracy of 5e-6 pixel on the location of a Nyquist sampled polychromatic point
spread function.
Methods: The interferometric calibration system produced modulated Young
fringes on the detector. The Young fringes were parametrized as products of
time and space dependent functions, based on various pixel parameters. The
minimization of func- tion parameters was done iteratively, until convergence
was obtained, revealing the pixel information needed for the calibration of
astrometric measurements.
Results: The calibration system yielded the pixel positions to an accuracy
estimated at 4e-4 pixel. After including the pixel position information, an
astrometric accuracy of 6e-5 pixel was obtained, for a PSF motion over more
than five pixels. In the static mode (small jitter motion of less than 1e-3
pixel), a photon noise limited precision of 3e-5 pixel was reached
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