Supernova neutrino halo and the suppression of self-induced flavor conversion

Neutrinos streaming from a supernova (SN) core occasionally scatter in the envelope, producing a small "neutrino halo" with a much broader angle distribution than the primary flux originating directly from the core. Cherry et al. (2012) have recently pointed out that, during the accretion phase, the halo actually dominates neutrino-neutrino refraction at distances exceeding some 100 km. However, the multiangle matter effect (which increases if the angle distribution is broader) still appears to suppress self-induced flavor conversion during the accretion phase.Comment: related to our previous PRL 108 (2012) 061101 [arXiv:1109.3601]; v2 with appendix on analytic treatment of halo, matches the published versio

Suppression of Self-Induced Flavor Conversion in the Supernova Accretion Phase

Self-induced flavor conversions of supernova (SN) neutrinos can strongly modify the flavor dependent fluxes. We perform a linearized flavor stability analysis with accretion-phase matter profiles of a 15 M_sun spherically symmetric model and corresponding neutrino fluxes. We use realistic energy and angle distributions, the latter deviating strongly from quasi-isotropic emission, thus accounting for both multi-angle and multi-energy effects. For our matter and neutrino density profile we always find stable conditions: flavor conversions are limited to the usual MSW effect. In this case one may distinguish the neutrino mass hierarchy in a SN neutrino signal if the mixing angle theta_13 is as large as suggested by recent experiments.Comment: 4 pages, 5 figures; minor edits, matches the version published in PR

High-resolution supernova neutrino spectra represented by a simple fit

To study the capabilities of supernova neutrino detectors, the instantaneous spectra are often represented by a quasi-thermal distribution of the form f(E) = E^alpha e^{-(alpha+1)E/E_{av}} where E_{av} is the average energy and alpha a numerical parameter. Based on a spherically symmetric supernova model with full Boltzmann neutrino transport we have, at a few representative post-bounce times, re-converged the models with vastly increased energy resolution to test the fit quality. For our examples, the spectra are well represented by such a fit in the sense that the counting rates for a broad range of target nuclei, sensitive to different parts of the spectrum, are reproduced very well. Therefore, the mean energy and root-mean-square energy of numerical spectra hold enough information to provide the correct alpha and to forecast the response of multi-channel supernova neutrino detection.Comment: 6 pages, including 4 figures and 2 tables. Clarifying paragraphs added; results unchanged. Matches published version in PR

On propagation failure in 1 and 2 dimensional excitable media

We present a non-perturbative technique to study pulse dynamics in excitable media. The method is used to study propagation failure in one-dimensional and two-dimensional excitable media. In one-dimensional media we describe the behaviour of pulses and wave trains near the saddle node bifurcation, where propagation fails. The generalization of our method to two dimensions captures the point where a broken front (or finger) starts to retract. We obtain approximate expressions for the pulse shape, pulse velocity and scaling behavior. The results are compared with numerical simulations and show good agreement.Comment: accepted for publication in Chao

A normal form for excitable media

We present a normal form for travelling waves in one-dimensional excitable media in form of a differential delay equation. The normal form is built around the well-known saddle-node bifurcation generically present in excitable media. Finite wavelength effects are captured by a delay. The normal form describes the behaviour of single pulses in a periodic domain and also the richer behaviour of wave trains. The normal form exhibits a symmetry preserving Hopf bifurcation which may coalesce with the saddle-node in a Bogdanov-Takens point, and a symmetry breaking spatially inhomogeneous pitchfork bifurcation. We verify the existence of these bifurcations in numerical simulations. The parameters of the normal form are determined and its predictions are tested against numerical simulations of partial differential equation models of excitable media with good agreement.Comment: 22 pages, accepted for publication in Chao

Struktur und Wirksamkeit arbeitsmarktpolitischer Qualifizierungsprogramme in Österreich

"Der Beitrag beschäftigt sich mit dem arbeitsmarktpolitischen Einsatz beruflicher Qualifizierungsmaßnahmen in außerbetrieblichen Einrichtungen in Österreich. Dieses zentrale arbeitsmarktpolitische Instrument diente bis weit in die zweite Hälfte der siebziger Jahre der Funktion der Aufstiegsförderung. Mit der Verschlechterung der Arbeitsmarktlage schob sich die Beschäftigungssicherung als neue Funktionsbestimmung zunehmend in den Vordergrund. Die wachsende Ausrichtung auf Zielgruppen mit besonderen Arbeitsmarktproblemen und der steigende Anteil von Auftragsmaßnahmen sind Ausdruck dieses Wandels. Im Rahmen einer repräsentativen längerfristigen Verbleibsanalyse werden personenbezogene Wirkungen der Teilnahme an derartigen Fördermaßnahmen vorgestellt. Ausgehend von den Zielsetzungen, die durch das Arbeitsmarktförderungsgesetz (AMFG) und entsprechende Durchführungsbestimmungen definiert sind, steht als objektiver Wirkungsindikator die Veränderung der Arbeitsmarktposition (Erwerbsstatus und Stabilität der Berufskarriere) im Vordergrund. Außerdem wird das subjektive Urteil der Teilnehmer zu verschiedenen Aspekten der Schulung und ihrer Wirkungen erhoben. Auf der Basis subjektiver und objektiver Befunde werden mehrdimensionale Erfolgsmuster ermittelt. Unterschiede in der Wirksamkeit der Schulungsmaßnahme für verschiedene Personengruppen und Kurstypen stellen einen zentralen Untersuchungsaspekt dar. Außerdem wird abzuschätzen versucht, inwieweit die Ergebnisse der Wirkungsanalyse von bestimmten Rahmenbedingungen beeinflußt werden." (Autorenrefarat)Qualifizierung - Programm, Arbeitsmarktpolitik - Auswirkungen, Teilnehmerstruktur, Beschäftigungseffekte, Teilnehmer - Einstellungen, Wirkungsforschung, Österreich

A test for a conjecture on the nature of attractors for smooth dynamical systems

Dynamics arising persistently in smooth dynamical systems ranges from regular dynamics (periodic, quasiperiodic) to strongly chaotic dynamics (Anosov, uniformly hyperbolic, nonuniformly hyperbolic modelled by Young towers). The latter include many classical examples such as Lorenz and H\'enon-like attractors and enjoy strong statistical properties. It is natural to conjecture (or at least hope) that most dynamical systems fall into these two extreme situations. We describe a numerical test for such a conjecture/hope and apply this to the logistic map where the conjecture holds by a theorem of Lyubich, and to the Lorenz-96 system in 40 dimensions where there is no rigorous theory. The numerical outcome is almost identical for both (except for the amount of data required) and provides evidence for the validity of the conjecture.Comment: Accepted version. Minor modifications from previous versio