Search results for "CONNECTION"
showing 10 items of 489 documents
Critical behavior of a supersymmetric extension of the Ginzburg-Landau model
2011
We make a connection between quantum phase transitions in condensed matter systems, and supersymmetric gauge theories that are of interest in the particle physics literature. In particular, we point out interesting effects of the supersymmetric quantum electrodynamics upon the critical behavior of the Ginzburg-Landau model. It is shown that supersymmetry fixes the critical exponents, as well as the Landau-Ginzburg parameter, and that the model resides in the type II regime of superconductivity.
Running Immirzi Parameter and Asymptotic Safety
2011
We explore the renormalization group (RG) properties of quantum gravity, using the vielbein and the spin connection as the fundamental field variables. We require the effective action to be invariant under the semidirect product of spacetime diffeomorphisms and local frame rotations. Starting from the corresponding functional integral we review the construction of an appropriate theory space and an exact funtional RG equation operating on it. We then solve this equation on a truncated space defined by a three parameter family of Holst-type actions which involve a running Immirzi parameter. We find evidence for the existence of an asymptotically safe fundamental theory. It is probably inequi…
Optimization of vehicle-trailer connection systems
2016
The three main requirements of a vehicle-trailer connection system are: en route stability, over- or under-steering restraint, minimum off-tracking along curved path. Linking the two units by four-bar trapeziums, wider stability margins may be attained in comparison with the conventional pintle-hitch for both instability types, divergent or oscillating. The stability maps are traced applying the Hurwitz method or the direct analysis of the characteristic equation at the instability threshold. Several types of four-bar linkages may be quickly tested, with the drawbars converging towards the trailer or the towing unit. The latter configuration appears preferable in terms of self-stability and…
“The first man on the street” - tracing a famous Hilbert quote (1900) back to Gergonne (1825)
2016
A short, catchy, and in its content somewhat exaggerated, quote allows us to draw a connection through three-quarters of a century between two leaders of mathematics who apparently held somewhat similar philosophical, pedagogical, and political views. In addition to providing some new facets to the biographies of Gergonne and Hilbert, our article relates to increasing demands for the dissemination of mathematical knowledge and to corresponding structural changes within mathematics during the 19th century.
Two new African and Madagascan species of the genus Holochlora (Orthoptera: Tettigoniidae, Phaneropterinae)
2017
Two new species, Holochlora mauritiana and H. ingrischi from the island of Mauritius and Zimbabwe, respectively, are described. Along with a third species, H. biloba Stål, 1874 from Madagascar, they are the sole African representatives of the mostly Oriental genus Holochlora Stål, 1873, including ca. 60 taxa distributed from India to China. Preliminary hypotheses on biogeographical and evolutionary origin of Afro-Madagascan Holochlora species are shortly discussed.
Invariant circles in the Bogdanov-Takens bifurcation for diffeomorphisms
1996
AbstractWe study a generic, real analytic unfolding of a planar diffeomorphism having a fixed point with unipotent linear part. In the analogue for vector fields an open parameter domain is known to exist, with a unique limit cycle. This domain is bounded by curves corresponding to a Hopf bifurcation and to a homoclinic connection. In the present case of analytic diffeomorphisms, a similar domain is shown to exist, with a normally hyperbolic invariant circle. It follows that all the ‘interesting’ dynamics, concerning the destruction of the invariant circle and the transition to trivial dynamics by the creation and death of homoclinic points, takes place in an exponentially small part of the…
Preliminary Tests On A Miniaturized Hybrid Pv-Pemfc System
2007
A regenerative hybrid PV-PEMFC low power system is a suitable solution to replace batteries and to supply small electric devices placed in remote areas with no grid connection. Such a system was designed and built including a PV array, electrolyzer, PEMFC stack (6We) and hydrogen storage tank. As well known a hybrid PV-PEMFC energy system may represent a reliable solution to the renewable energy storage problem. Hydrogen produced by such a system is a clean fuel, suitable to replace traditional fuels which contain carbon damaging the environment. The paper reports results of a preliminary, non-dynamic experimental analysis performed on the system in order to study the effects of the anode p…
Infilled frames: Developments in the evaluation of cyclic behaviour under lateral loads
2005
In order to consider the modified seismic response of framed structures in the presence of masonry infills, proper models have to be formulated. Because of the complexity of the problem, a careful definition of an equivalent diagonal pin-jointed strut, able to represent the horizontal force-interstorey displacement cyclic law of the actual infill, may be a solution. In this connection the present paper, continuing a previous work in which a generalised criterion for the determination of the ideal cross-section of the equivalent strut was formulated, analizes some models known in literature for the prediction of the lateral cyclic behaviour discussing their field of validity. As a support of…
Off the grid. Touristische Idyllen der Entnetzung
2021
Abstract The article examines the relation of tourism and idyll in regard to the mediation of the tourist experience. Digital detox tourism and off grid tourism are two examples of contemporary tourism – including their respective practices and ways of promotion – that associate certain cultural stereotypes with the idyll. While digital detox tourism promises independence from the digital world, off grid tourism detaches the tourist from infrastructure and supplies. Paradoxically, the advertising of these types of ‘disconnection’ makes use of the same linked infrastructures that tourists are bound to leave behind. Thus, this article reveals the ways in which digital detox tourism and off gr…