4,891 research outputs found
Solidifying system of democracy in the Central and Eastern European new EU members
The paper examines the requirements of an effective and legitimized democratic political system in the process of transition. The analysis and the conclusions are based on the Hungarian experience, which can carefully be applied to all Central and Eastern European (CEE) countries. Special focus is given to the relationship of legal certainty and the efficiency of the democratic system, to the tension between legalism and managerialism and to the characteristics of civil society organizations. In the conclusion special features of the transitional countries are pointed out
Superconductors with Magnetic Impurities: Instantons and Sub-gap States
When subject to a weak magnetic impurity potential, the order parameter and
quasi-particle energy gap of a bulk singlet superconductor are suppressed.
According to the conventional mean-field theory of Abrikosov and Gor'kov, the
integrity of the energy gap is maintained up to a critical concentration of
magnetic impurities. In this paper, a field theoretic approach is developed to
critically analyze the validity of the mean field theory. Using the
supersymmetry technique we find a spatially homogeneous saddle-point that
reproduces the Abrikosov-Gor'kov theory, and identify instanton contributions
to the density of states that render the quasi-particle energy gap soft at any
non-zero magnetic impurity concentration. The sub-gap states are associated
with supersymmetry broken field configurations of the action. An analysis of
fluctuations around these configurations shows how the underlying supersymmetry
of the action is restored by zero modes. An estimate of the density of states
is given for all dimensionalities. To illustrate the universality of the
present scheme we apply the same method to study `gap fluctuations' in a normal
quantum dot coupled to a superconducting terminal. Using the same instanton
approach, we recover the universal result recently proposed by Vavilov et al.
Finally, we emphasize the universality of the present scheme for the
description of gap fluctuations in d-dimensional superconducting/normal
structures.Comment: 18 pages, 9 eps figure
Development of a cometosheath at comet 67P/Churuyumov-Gerasimenko: A case study comparison of Rosetta observations
Context: The ionosphere of a comet is known to deflect the solar wind through
mass loading, but the interaction is dependent on cometary activity. We
investigate the details of this process at comet 67P using the Rosetta Ion
Composition Analyzer. Aims: This study aims to compare the interaction of the
solar wind and cometary ions during two different time periods in the Rosetta
mission. Methods: We compared both the integrated ion moments (density,
velocity, and momentum flux) and the velocity distribution functions for two
days, four months apart. The velocity distribution functions were projected
into a coordinate system dependent on the magnetic field direction and averaged
over three hours. Results: The first case shows highly scattered H+ in both ion
moments and velocity distribution function. The He2+ ions are somewhat
scattered, but less so, and appear more like those of H2O+ pickup ions. The
second case shows characteristic evidence of mass-loading, where the solar wind
species are deflected, but the velocity distribution function is not
significantly changed. Conclusions: The distributions of H+ in the first case,
when compared to He2+ and H2O+ pickup ions, are indicative of a narrow
cometosheath on the scale of the H+ gyroradius. Thus, He2+ and H2O+, with
larger gyroradii, are largely able to pass through this cometosheath. An
examination of the momentum flux tensor suggests that all species in the first
case have a significant non-gyrotropic momentum flux component that is higher
than that of the second mass-loaded case. Mass loading is not a sufficient
explanation for the distribution functions and momentum flux tensor in the
first case, and so we assume this is evidence of bow shock formation.Comment: 14 pages, 9 figures, 3 tables, 2 video
Improving LIGO calibration accuracy by tracking and compensating for slow temporal variations
Calibration of the second-generation LIGO interferometric gravitational-wave
detectors employs a method that uses injected periodic modulations to track and
compensate for slow temporal variations in the differential length response of
the instruments. These detectors utilize feedback control loops to maintain
resonance conditions by suppressing differential arm length variations. We
describe how the sensing and actuation functions of these servo loops are
parameterized and how the slow variations in these parameters are quantified
using the injected modulations. We report the results of applying this method
to the LIGO detectors and show that it significantly reduces systematic errors
in their calibrated outputs.Comment: 13 pages, 8 figures. This is an author-created, un-copyedited version
of an article published in Classical and Quantum Gravity. IOP Publishing Ltd
is not responsible for any errors or omissions in this version of the
manuscript or any version derived from i
Gravitational waves from Sco X-1: A comparison of search methods and prospects for detection with advanced detectors
The low-mass X-ray binary Scorpius X-1 (Sco X-1) is potentially the most
luminous source of continuous gravitational-wave radiation for interferometers
such as LIGO and Virgo. For low-mass X-ray binaries this radiation would be
sustained by active accretion of matter from its binary companion. With the
Advanced Detector Era fast approaching, work is underway to develop an array of
robust tools for maximizing the science and detection potential of Sco X-1. We
describe the plans and progress of a project designed to compare the numerous
independent search algorithms currently available. We employ a mock-data
challenge in which the search pipelines are tested for their relative
proficiencies in parameter estimation, computational efficiency, robust- ness,
and most importantly, search sensitivity. The mock-data challenge data contains
an ensemble of 50 Scorpius X-1 (Sco X-1) type signals, simulated within a
frequency band of 50-1500 Hz. Simulated detector noise was generated assuming
the expected best strain sensitivity of Advanced LIGO and Advanced VIRGO ( Hz). A distribution of signal amplitudes was then
chosen so as to allow a useful comparison of search methodologies. A factor of
2 in strain separates the quietest detected signal, at
strain, from the torque-balance limit at a spin frequency of 300 Hz, although
this limit could range from (25 Hz) to (750 Hz) depending on the unknown frequency of Sco X-1. With future
improvements to the search algorithms and using advanced detector data, our
expectations for probing below the theoretical torque-balance strain limit are
optimistic.Comment: 33 pages, 11 figure
Excessive boredom among adolescents: A comparison between low and high achievers
Existing research shows that high achievement boredom is correlated with a range of undesirable behavioral and personality variables and that the main antecedents of boredom are being over- or under-challenged. However, merely knowing that students are highly bored, without taking their achievement level into account, might be insufficient for drawing conclusions about students' behavior and personality. We, therefore, investigated if low- vs. high-achieving students who experience strong mathematics boredom show different behaviors and personality traits. The sample consisted of 1,404 German secondary school students (fifth to 10th grade, mean age 12.83 years, 52% female). We used self-report instruments to assess boredom in mathematics, behavioral (social and emotional problems, positive/negative affect, cognitive reappraisal, and expressive suppression), and personality variables (neuroticism and conscientiousness). In comparing highly bored students (more than one SD above M, n = 258) who were low vs. high achievers (as indicated by the math grade, n = 125 / n = 119), results showed that there were no mean level differences across those groups for all variables. In conclusion, our results suggest that high boredom can occur in both low- and high-achieving students and that bored low- and high-achievers show similar behaviors and personality profiles
Reconstructing the calibrated strain signal in the Advanced LIGO detectors
Advanced LIGO's raw detector output needs to be calibrated to compute
dimensionless strain h(t). Calibrated strain data is produced in the time
domain using both a low-latency, online procedure and a high-latency, offline
procedure. The low-latency h(t) data stream is produced in two stages, the
first of which is performed on the same computers that operate the detector's
feedback control system. This stage, referred to as the front-end calibration,
uses infinite impulse response (IIR) filtering and performs all operations at a
16384 Hz digital sampling rate. Due to several limitations, this procedure
currently introduces certain systematic errors in the calibrated strain data,
motivating the second stage of the low-latency procedure, known as the
low-latency gstlal calibration pipeline. The gstlal calibration pipeline uses
finite impulse response (FIR) filtering to apply corrections to the output of
the front-end calibration. It applies time-dependent correction factors to the
sensing and actuation components of the calibrated strain to reduce systematic
errors. The gstlal calibration pipeline is also used in high latency to
recalibrate the data, which is necessary due mainly to online dropouts in the
calibrated data and identified improvements to the calibration models or
filters.Comment: 20 pages including appendices and bibliography. 11 Figures. 3 Table
Investigating short-time-scale variations in cometary ions around comet 67P
The highly varying plasma environment around comet 67P/Churyumov–Gerasimenko inspired an upgrade of the ion mass spectrometer (Rosetta Plasma Consortium Ion Composition Analyzer) with new operation modes, to enable high time resolution measurements of cometary ions. Two modes were implemented, one having a 4 s time resolution in the energy range 0.3–82 eV/q and the other featuring a 1 s time resolution in the energy range 13–50 eV/q. Comparing measurements made with the two modes, it was concluded that 4 s time resolution is enough to capture most of the fast changes of the cometary ion environment. The 1462 h of observations done with the 4 s mode were divided into hour-long sequences. It is possible to sort 84 per cent of these sequences into one of five categories, depending on their appearance in an energy–time spectrogram. The ion environment is generally highly dynamic, and variations in ion fluxes and energies are seen on time-scales of 10 s to several minutes
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