2,680 research outputs found
Islam, Religiosity, and Immigrant Political Action in Western Europe
Cataloged from PDF version of article.The issues of migration and immigrant political integration in western democracies have
become increasingly intertwined with debates on religion, particularly Islam. To date, however,
we have surprisingly little systematic research on how religious beliefs are related to
immigrants’ political engagement. In this study, we argue that religion has a capacity to
mobilize immigrants politically but the strength of this relationship depends on immigrant
generation, religiosity, and the type of religion. Using survey data collected as part of the
European Social Survey (ESS) 2002–2010 in 18 West European democracies, our analyses
reveal that religion is indeed linked to political engagement of immigrants in a complex
way: while belonging to a religion is generally associated with less political participation,
exposure to religious institutions appears to have the opposite effect. Moreover, we find
that, compared to foreign-born Muslims, second-generation Muslim immigrants are not
only more religious and more politically dissatisfied with their host countries, but also that
religiosity is more strongly linked to their political engagement. This relationship, however,
is limited to uninstitutionalized political action
Time--delay autosynchronization of the spatio-temporal dynamics in resonant tunneling diodes
The double barrier resonant tunneling diode exhibits complex spatio-temporal
patterns including low-dimensional chaos when operated in an active external
circuit. We demonstrate how autosynchronization by time--delayed feedback
control can be used to select and stabilize specific current density patterns
in a noninvasive way. We compare the efficiency of different control schemes
involving feedback in either local spatial or global degrees of freedom. The
numerically obtained Floquet exponents are explained by analytical results from
linear stability analysis.Comment: 10 pages, 16 figure
Pitch discriminiation accuracy in musicians vs nonmusicians: an event-related potential and behavioral study
Previously, professional violin players were found to automatically discriminate tiny pitch changes, not discriminable by nonmusicians. The present study addressed the pitch processing accuracy in musicians with expertise in playing a wide selection of instruments (e.g., piano; wind and string instruments). Of specific interest was whether also musicians with such divergent backgrounds have facilitated accuracy in automatic and/or attentive levels of auditory processing. Thirteen professional musicians and 13 nonmusicians were presented with frequent standard sounds and rare deviant sounds (0.8, 2, or 4% higher in frequency). Auditory event-related potentials evoked by these sounds were recorded while first the subjects read a self-chosen book and second they indicated behaviorally the detection of sounds with deviant frequency. Musicians detected the pitch changes faster and more accurately than nonmusicians. The N2b and P3 responses recorded during attentive listening had larger amplitude in musicians than in nonmusicians. Interestingly, the superiority in pitch discrimination accuracy in musicians over nonmusicians was observed not only with the 0.8% but also with the 2% frequency changes. Moreover, also nonmusicians detected quite reliably the smallest pitch changes of 0.8%. However, the mismatch negativity (MMN) and P3a recorded during a reading condition did not differentiate musicians and nonmusicians. These results suggest that musical expertise may exert its effects merely at attentive levels of processing and not necessarily already at the preattentive levels
Time-delayed feedback control in astrodynamics
In this paper we present time-delayed feedback control (TDFC) for the purpose of autonomously driving trajectories of nonlinear systems into periodic orbits. As the generation of periodic orbits is a major component of many problems in astodynamics we propose this method as a useful tool in such applications. To motivate the use of this method we apply it to a number of well known problems in the astrodynamics literature. Firstly, TDFC is applied to control in the chaotic attitude motion of an asymmetric satellite in an elliptical orbit. Secondly, we apply TDFC to the problem of maintaining a spacecraft in a periodic orbit about a body with large ellipticity (such as an asteroid) and finally, we apply TDFC to eliminate the drift between two satellites in low Earth orbits to ensure their relative motion is bounded
Dynamical Friction in a Gaseous Medium
Using time-dependent linear perturbation theory, we evaluate the dynamical
friction force on a massive perturber M_p traveling at velocity V through a
uniform gaseous medium of density rho_0 and sound speed c_s. This drag force
acts in the direction -\hat V, and arises from the gravitational attraction
between the perturber and its wake in the ambient medium. For supersonic motion
(M=V/c_s>1), the enhanced-density wake is confined to the Mach cone trailing
the perturber; for subsonic motion (M<1), the wake is confined to a sphere of
radius c_s t centered a distance V t behind the perturber. Inside the wake,
surfaces of constant density are hyperboloids or oblate spheroids for
supersonic or subsonic perturbers, respectively, with the density maximal
nearest the perturber. The dynamical drag force has the form F_df= - I 4\pi (G
M_p)^2\rho_0/V^2. We evaluate I analytically; its limits are I\to M^3/3 for
M>1. We compare our results to the
Chandrasekhar formula for dynamical friction in a collisionless medium, noting
that the gaseous drag is generally more efficient when M>1 but less efficient
when M<1. To allow simple estimates of orbit evolution in a gaseous protogalaxy
or proto-star cluster, we use our formulae to evaluate the decay times of a
(supersonic) perturber on a near-circular orbit in an isothermal \rho\propto
r^{-2} halo, and of a (subsonic) perturber on a near-circular orbit in a
constant-density core. We also mention the relevance of our calculations to
protoplanet migration in a circumstellar nebula.Comment: 17 pages, 5 postscript figures, to appear in ApJ 3/1/9
Coherence resonance in a network of FitzHugh-Nagumo systems: interplay of noise, time-delay and topology
We systematically investigate the phenomena of coherence resonance in
time-delay coupled networks of FitzHugh-Nagumo elements in the excitable
regime. Using numerical simulations, we examine the interplay of noise,
time-delayed coupling and network topology in the generation of coherence
resonance. In the deterministic case, we show that the delay-induced dynamics
is independent of the number of nearest neighbors and the system size. In the
presence of noise, we demonstrate the possibility of controlling coherence
resonance by varying the time-delay and the number of nearest neighbors. For a
locally coupled ring, we show that the time-delay weakens coherence resonance.
For nonlocal coupling with appropriate time-delays, both enhancement and
weakening of coherence resonance are possible
On the Mechanism of Time--Delayed Feedback Control
The Pyragas method for controlling chaos is investigated in detail from the
experimental as well as theoretical point of view. We show by an analytical
stability analysis that the revolution around an unstable periodic orbit
governs the success of the control scheme. Our predictions concerning the
transient behaviour of the control signal are confirmed by numerical
simulations and an electronic circuit experiment.Comment: 4 pages, REVTeX, 4 eps-figures included Phys. Rev. Lett., in press
also available at
http://athene.fkp.physik.th-darmstadt.de/public/wolfram.htm
The natural science of cosmology
The network of cosmological tests is tight enough now to show that the
relativistic Big Bang cosmology is a good approximation to what happened as the
universe expanded and cooled through light element production and evolved to
the present. I explain why I reach this conclusion, comment on the varieties of
philosophies informing searches for a still better cosmology, and offer an
example for further study, the curious tendency of some classes of galaxies to
behave as island universes.Comment: Keynote lecture at the seventh International Conference on
Gravitation and Cosmology, Goa India, December 201
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