1,427 research outputs found
Modulation equations near the Eckhaus boundary: the KdV equation
We are interested in the description of small modulations in time and space
of wave-train solutions to the complex Ginzburg-Landau equation \begin{align*}
\partial_T \Psi = (1+ i \alpha) \partial_X^2 \Psi + \Psi - (1+i \beta ) \Psi
|\Psi|^2, \end{align*} near the Eckhaus boundary, that is, when the wave train
is near the threshold of its first instability. Depending on the parameters , a number of modulation equations can be derived, such as
the KdV equation, the Cahn-Hilliard equation, and a family of Ginzburg-Landau
based amplitude equations. Here we establish error estimates showing that the
KdV approximation makes correct predictions in a certain parameter regime. Our
proof is based on energy estimates and exploits the conservation law structure
of the critical mode. In order to improve linear damping we work in spaces of
analytic functions.Comment: 44 pages, 8 figure
Impact of atmospheric turbulence on geodetic very long baseline interferometry
We assess the impact of atmospheric turbulence on geodetic very long baseline interferometry (VLBI) through simulations of atmospheric delays. VLBI observations are simulated for the two best existing VLBI data sets: The continuous VLBI campaigns CONT05 and CONT08. We test different methods to determine the magnitude of the turbulence above each VLBI station, i.e., the refractive index structure constant C-n(2). The results from the analysis of the simulated data and the actually observed VLBI data are compared. We find that atmospheric turbulence today is the largest error source for geodetic VLBI. Accurate modeling of atmospheric turbulence is necessary to reach the highest accuracy with geodetic VLBI
Decarbonizing Transport in the European Union: Emission Performance Standards and the Perspectives for a European Green Deal
The transport sector is a major driver of climate change both globally and in the European Union (EU). While the EU as a whole is showing declining carbon emissions, transport-related emissions are higher than in 1990. Car traffic is responsible for around 12 percent of the EU’s total greenhouse gas emissions. EU Commission President Ursula von der Leyen underlined the efforts to strengthen the decarbonization of the EU at the end of 2019 by publishing the European Green Deal (EGD) communication. In this paper, we analyze the controversy surrounding the emission performance standards for cars adopted in spring 2019. Car manufacturers must reduce the average carbon emissions of their fleets by 37.5% between 2021 and 2030. In this respect, the new emission performance standards are more ambitious than the previous ones. However, our argument is that without a major shift in the balance of power, extensive decarbonization and a departure from car-centered transport development will not be possible. Therefore, it is crucial for mobility research to critically engage with lobbying power in the EU and with concepts such as environmental leadership, which often underexpose the structural power of incumbent actors and existing path dependencies
Greening the Car? Conflict Dynamics within the German Platform for Electric Mobility
The environmental crisis due to air pollution, high CO2 emissions, noise from traffic and soil ceiling requires profound changes to the car-dependent transport system. This article examines the political dynamics of German transport politics, focusing on the National Platform for Electric Mobility (NPE), a high-level political forum that aimed to accelerate the run-up of the electric mobility market in Germany. The NPE provides an interesting case to study the strategies of stakeholders in influencing policy-making and shaping alternative pathways to the car-centered transport system. The paper focusses on actor constellations and the conflicts that arise within the NPE, as well as the temporal dynamics within the electric mobility debate. The findings suggest that the NPE contributed to a narrow understanding of mobility transformation based on road transport and electric cars, but that it is better described as ecological modernization. Within this narrow framework, a fundamental conflict unfolds between strong advocates versus those slowing down the ecological modernization of the car. A third group demands at least a partial departure from the automobile-centered model but remains marginalized within the NPE. Aside from this core conflict, members of the NPE struggled over the location for battery cell production, the introduction of a purchase grant known as the environmental bonus, and the expansion of battery recharging infrastructure. These issues illustrate that discussions within the NPE relate to the political debates about the future of mobility, which have intensified in Germany in recent years. However, the case of the NPE shows that high-level stakeholder platforms are not an adequate forum to legitimately deliberate and to practically contribute to a wider and more fundamental rethink of future mobility concepts. View Full-Tex
Fidelity approach to the disordered quantum XY model
We study the random XY spin chain in a transverse field by analyzing the
susceptibility of the ground state fidelity, numerically evaluated through a
standard mapping of the model onto quasi-free fermions. It is found that the
fidelity susceptibility and its scaling properties provide useful information
about the phase diagram. In particular it is possible to determine the Ising
critical line and the Griffiths phase regions, in agreement with previous
analytical and numerical results.Comment: 4 pages, 3 figures; references adde
Assessment of Physical Activity Patterns in Adolescent Patients With Anorexia Nervosa and Their Effect on Weight Gain
(1) Background: Altered physical activity (PA) affects weight recovery in anorexia nervosa (AN) patients. The study aimed to objectively characterize PA patterns and their effect on weight trajectory in adolescent AN patients.
(2) Methods: PA was assessed in 47 patients on admission to inpatient treatment, in n = 25 of these patients again 4 weeks after discharge (follow-up, FU), as well as in 20 adolescent healthy controls using the Sense Wear™ armband. The following PA categories were defined by metabolic equivalent (MET) ranges: sedentary behavior (SB), light (LPA), moderate (MPA), vigorous (VPA), and high-level PA (HLPA= MPA + VPA).
(3) Results: LPA on admission was significantly higher in AN patients than in controls (103 vs. 55 min/d, p < 0.001), and LPA in AN decreased over time to 90 min/d (p = 0.006). Patients with higher admission LPA (n = 12) still had elevated LPA at FU (p = 0.003). High admission LPA was associated with a higher inpatient BMI percentage gain (ΔBMI%; 18.2% ± 10.0% vs. 12.0% ± 9.7%, p = 0.037) but with a loss of ΔBMI% at FU (-2.3% ± 3.6% vs. 0.8% ± 3.6%, p = 0.045). HLPA at baseline was associated with a lower inpatient ΔBMI% (p = 0.045).
(4) Conclusion: Elevated LPA in AN patients decreased after inpatient treatment, and PA patterns had an impact on weight trajectory
Event Indexing Systems for Efficient Selection and Analysis of HERA Data
The design and implementation of two software systems introduced to improve
the efficiency of offline analysis of event data taken with the ZEUS Detector
at the HERA electron-proton collider at DESY are presented. Two different
approaches were made, one using a set of event directories and the other using
a tag database based on a commercial object-oriented database management
system. These are described and compared. Both systems provide quick direct
access to individual collision events in a sequential data store of several
terabytes, and they both considerably improve the event analysis efficiency. In
particular the tag database provides a very flexible selection mechanism and
can dramatically reduce the computing time needed to extract small subsamples
from the total event sample. Gains as large as a factor 20 have been obtained.Comment: Accepted for publication in Computer Physics Communication
General class of continuous variable entanglement criteria
We present a general class of entanglement criteria for continuous variable
systems. Our criteria are based on the Husimi -distribution and allow for
optimization over the set of all concave functions rendering them extremely
general and versatile. We show that several entropic criteria and second moment
criteria are obtained as special cases. Our criteria reveal entanglement of
families of states undetected by any commonly used criteria and provide clear
advantages under typical experimental constraints such as finite detector
resolution and measurement statistics.Comment: 5 pages, 4 figures, published versio
Detecting continuous variable entanglement in phase space with the -distribution
We prove a general class of continuous variable entanglement criteria based
on the Husimi -distribution, which represents a quantum state in canonical
phase space, by employing a theorem by Lieb and Solovej. We discuss their
generality, which roots in the possibility to optimize over the set of concave
functions, from the perspective of continuous majorization theory and show that
with this approach families of entropic as well as second moment criteria
follow as special cases. All derived criteria are compared to corresponding
marginal based criteria and the strength of the phase space approach is
demonstrated for a family of prototypical example states where only our
criteria flag entanglement. Further, we explore their optimization prospects in
two experimentally relevant scenarios characterized by sparse data: finite
detector resolution and finite statistics. In both scenarios optimization leads
to clear improvements enlarging the class of detected states and the
signal-to-noise ratio of the detection, respectively.Comment: 23 pages, 11 figures, published versio
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