2,057 research outputs found
Robert Neumann: Mit eigener Feder
No full textRobert Neumann (1897–1957, Austrian exiled author and Vicepresidet of the PEN International, was even a disputatious antifascist political writer. His essays, his letters and biograpical documents give a vivid portrait of the diversity of literary life in Germay and Austria (before 1933/after 1958) and of exile in England (1933–1958).Der österreichische Schriftsteller Robert Neumann (1897–1975), Exilant und Vizepräsident des PEN International, war auch ein streitbarer antifaschistischer Publizist. Seine politisch-literarischen Aufsätze, seine Briefe und biographischen Dokumente ergeben ein lebendiges und facettenreiches Bild des literarischen Lebens in Deutschland und Österreich (vor 1933/nach 1958) und des Exils in England (1933–1958)
Relative Haagerup property for arbitrary von Neumann algebras
No full textWe introduce the relative Haagerup approximation property for a unital, expected inclusion of arbitrary von Neumann algebras and show that if the smaller algebra is finite then the notion only depends on the inclusion itself, and not on the choice of the conditional expectation. Several variations of the definition are shown to be equivalent in this case, and in particular the approximating maps can be chosen to be unital and preserving the reference state. The concept is then applied to amalgamated free products of von Neumann algebras and used to deduce that the standard Haagerup property for a von Neumann algebra is stable under taking free products with amalgamation over finite-dimensional subalgebras. The general results are illustrated by examples coming from q-deformed Hecke-von Neumann algebras and von Neumann algebras of quantum orthogonal groups.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Analysi
A comparison of deflation and the balancing Neumann-Neumann preconditioner
No full textIn this paper we compare various preconditioners for the numerical solution of partial differential equations. We compare the well-known balancing Neumann Neumann preconditioner used in domain decomposition methods with a so-called deflation preconditioner. We prove that the effective condition number of the deflated preconditioned system is always, i.e. for all deflation vectors and all restrictions and prolongations, below the condition number of the system preconditioned by the balancing Neumann-Neumann preconditioner. Even more, we establish that both preconditioners lead to almost the same spectra. The zero eigenvalues of the deflation preconditioned system are replaced by eigenvalues which are one if the balancing Neumann-Neumann preconditioner is used. Moreover, we proved that the A-norm of the errors of the iterates build by the deflation preconditioner is always below the A-norm of the errors of the iterates build by the balancing Neumann-Neumann preconditioner. Additionally, the amount of work of one iteration of the de ation preconditioned system is less than the amount of work of one iteration of the balancing Neumann-Neumann preconditioned system. Finally, we establish that the deflation preconditioner and the balancing Neumann-Neumann preconditioner produces the same iterates if one uses certain starting vectors. Numerical results for porous media flows emphasize the theoretical results.Electrical Engineering, Mathematics and Computer Scienc
Temporal dynamics and fitness consequences of coalition formation in male primates
No full textCoalition formation is one of the most striking forms of cooperation found in animals. Yet, there is substantial variation between taxa regarding the mechanisms by which coalitions can result in fitness consequences. Here, we investigate the influence of coalitions on dominance rank trajectories and subsequently on reproductive success in wild male crested macaques (Macaca nigra) at Tangkoko Nature Reserve (Sulawesi, Indonesia). We observed 128 coalition events involving 28 males and tested how a variety of coalition properties and factors related to the social environment influenced future male rank. We further used genetic paternity analysis of 19 infants conceived during the study to assess male reproductive success. Our results show that males participating in coalitions achieved higher-than-expected future ranks, while coalition targets had lower-than-expected future ranks. Additionally, all-up coalitions had stronger effects on rank than all-down and bridging coalitions, and these were modulated by the relative strength of coalition partners versus targets. Finally, higher ranking males were more likely to sire infants than lower ranking males. These results provide important insights regarding the mechanisms underlying coalition formation and support the idea that one major path by which coalitions can affect fitness is through influencing male dominance trajectories
Efficient Itô diffusions on Riemannian manifolds
No full textA generalization of Donsker’s theorem states that, under mild conditions, Itô diffusions
on complete Riemannian manifolds can be approximated by geodesic random walks. Generally,
this does not provide an efficient way of simulating Itô diffusions on Riemannian
manifolds, since a non-linear differential equation must be solved at every step. In the
special case of Brownian motion on a compact manifold, approximate geodesic random
walks based on approximations of the exponential map called retractions have been proposed
and shown to be efficiently computable and convergent to Brownian motion. Using
the theory of Feller processes, we generalize the method of retraction-based random walks
and its convergence results to Itô diffusions on compact Riemannian manifolds under mild
assumptions on the drift and diffusion terms
Sub-Riemannian Random Walks: From Connections to Retractions
No full textWe study random walks on sub-Riemannian manifolds using the framework of retractions, i.e., approximations of normal geodesics. We show that such walks converge to the correct horizontal Brownian motion if normal geodesics are approximated to at least second order. In particular, we (i) provide conditions for convergence of geodesic random walks defined with respect to normal, compatible, and partial connections and (ii) provide examples of computationally efficient retractions, e.g., for simulating anisotropic Brownian motion on Riemannian manifolds
Sub-Riemannian Random Walks: From Connections to Retractions
No full textWe study random walks on sub-Riemannian manifolds using the framework of retractions, i.e., approximations of normal geodesics. We show that such walks converge to the correct horizontal Brownian motion if normal geodesics are approximated to at least second order. In particular, we (i) provide conditions for convergence of geodesic random walks defined with respect to normal, compatible, and partial connections and (ii) provide examples of computationally efficient retractions, e.g., for simulating anisotropic Brownian motion on Riemannian manifolds
Efficient Itô diffusions on Riemannian manifolds
No full textA generalization of Donsker’s theorem states that, under mild conditions, Itô diffusions
on complete Riemannian manifolds can be approximated by geodesic random walks. Generally,
this does not provide an efficient way of simulating Itô diffusions on Riemannian
manifolds, since a non-linear differential equation must be solved at every step. In the
special case of Brownian motion on a compact manifold, approximate geodesic random
walks based on approximations of the exponential map called retractions have been proposed
and shown to be efficiently computable and convergent to Brownian motion. Using
the theory of Feller processes, we generalize the method of retraction-based random walks
and its convergence results to Itô diffusions on compact Riemannian manifolds under mild
assumptions on the drift and diffusion terms
Werner Helsper/ Lena Dreier/ Anja Gibson/ Katrin Kotzyba/ Mareke Niemann: Exklusive Gymnasien und ihre Schüler. Passungsverhältnisse zwischen institutionellem und individuellem Schülerhabitus. Wiesbaden: VS Verlag für Sozialwissenschaften 2017 (537 S.) [Rezension]
No full textRezension von: Werner Helsper/ Lena Dreier/ Anja Gibson/ Katrin Kotzyba/ Mareke Niemann: Exklusive Gymnasien und ihre Schüler. Passungsverhältnisse zwischen institutionellem und individuellem Schülerhabitus. Wiesbaden: VS Verlag für Sozialwissenschaften 2017 (537 S.; ISBN 978-3-658-17079-0; 69,99 EUR)
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