11,257 research outputs found
Timelike self-similar spherically symmetric perfect-fluid models
Einstein's field equations for timelike self-similar spherically symmetric
perfect-fluid models are investigated. The field equations are rewritten as a
first-order system of autonomous differential equations. Dimensionless
variables are chosen in such a way that the number of equations in the coupled
system is reduced as far as possible and so that the reduced phase space
becomes compact and regular. The system is subsequently analysed qualitatively
using the theory of dynamical systems.Comment: 23 pages, 6 eps-figure
Ein Ur III-Text aus Münsteraner Privatbesitz
Uppsatsen behandlar hur USA: s president George W Bush använder civilreligiösa inslag i sin retorik under sitt första år som president. Han startade ämbetsperioden med att använda religiösa anspelningar i sitt installationstal., för att sedan fortsätta i samma anda hela året. Bush är inte den första presidenten att använda sådana retoriska knep. Ända sedan USA: s grundande har presidenterna förstärkt sin talarkonst genom att hänvisa till Gud och att landet är utvalt av Gud - ett nytt Israel. Landets presidenter har alltid varit mer eller mindre övertygade om att Gud står på USA: s sida. Detta trots att det första tillägget i USA: s konstitution föreskriver en separation mellan religion ochstat. Uppsatsen analyseras utifrån en innehållsanalys, som är en vanlig metod för att analysera politiska tal. Vår innehållsanalys består av åtta olika kategorier som speglar Bushs civilreligiösa retorik väl. Resultatet visar att Bush som president anser att det är självklart att en amerikansk president har en gudstro. Han använder ett religiöst språkbruk genom att citera ur Bibeln och Koranen i sina offentliga framträdanden. Han säger sig vara övertygad om att USA är utvalt av Gud att styra över världen. En stor del av Bushs civilreligiösa retorik går att hitta i att han försöker ena nationen genom att hänvisa till landets historia. Han visar ofta hur krigshjältar och presidenter har offrat sina liv för USA. Vi anser att Bush använder civilreligiös retorik för att ena nationen vid svåra tillfällen. Efter terrorattacken den 11: e september 2001 ökar frekvensen av civilreligion hos Bush. Det är tydligt att den amerikanske presidenten vill ena en nation i chock. Vi menar också att det av tradition förväntas att USA:s president har ett civilreligiöst språkbruk. Vi menar att Bush använder civilreligionen som en ursäkt för att inte genomföra reella politiska förändringar i samhället
Chiral surfaces self-assembling in one-component systems with isotropic interactions
We show that chiral symmetry can be broken spontaneously in one-component
systems with isotropic interactions, i.e. many-particle systems having maximal
a priori symmetry. This is achieved by designing isotropic potentials that lead
to self-assembly of chiral surfaces. We demonstrate the principle on a simple
chiral lattice and on a more complex lattice with chiral super-cells. In
addition we show that the complex lattice has interesting melting behavior with
multiple morphologically distinct phases that we argue can be qualitatively
predicted from the design of the interaction.Comment: 4 pages, 4 figure
Spatially self-similar spherically symmetric perfect-fluid models
Einstein's field equations for spatially self-similar spherically symmetric
perfect-fluid models are investigated. The field equations are rewritten as a
first-order system of autonomous differential equations. Dimensionless
variables are chosen in such a way that the number of equations in the coupled
system is reduced as far as possible and so that the reduced phase space
becomes compact and regular. The system is subsequently analysed qualitatively
with the theory of dynamical systems.Comment: 21 pages, 6 eps-figure
Light-cone analysis of ungauged and topologically gauged BLG theories
We consider three-dimensional maximally superconformal
Bagger-Lambert-Gustavsson (BLG) theory and its topologically gauged version
(constructed recently in arXiv:0809.4478 [hep-th]) in the light-cone gauge.
After eliminating the entire Chern-Simons gauge field, the ungauged BLG theory
looks more conventional and, apart from the order of the interaction terms,
resembles N=4 super-Yang-Mills theory in four dimensions. The light-cone
superspace version of the BLG theory is given to quadratic and quartic order
and some problems with constructing the sixth order interaction terms are
discussed. In the topologically gauged case, we analyze the field equations
related to the three Chern-Simons type terms of N=8 conformal supergravity and
discuss some of the special features of this theory and its couplings to BLG.Comment: 22 pages; v2 some typos correcte
The Dynamics, Prevalence and Impact of Nematode Infections in Organically Raised Sheep in Sweden
A three-year survey (1997–99) was carried out on organically reared sheep flocks throughout Sweden. The aim was to determine the prevalence and intensity of nematode infections and to establish relationships between sheep management practices and parasite infections. Faecal samples from ewes and lambs were collected from 152 organic flocks around lambing-time and during the grazing-period for analysis. Results were compared with the different management practices that farmers use to prevent parasitism in their flocks. A high proportion of the flocks was infected with nematodes. The most prevalent species were Haemonchus contortus, Teladorsagia circumeincta, Trichostrongylus axei, T. colubriformis and Chabertia ovina and infections progressively increased during summer in lambs grazing on permanent pastures. Severity of parasitic infection in lambs was highly dependent on egg output from the ewes. H. contortus was found in 37% of the flocks, even at latitudes approximating the Polar Circle. Nematodirus battus was recorded for the first time in Sweden during the course of this study. Lambs turned out onto permanent pasture showed higher nematode faecal egg counts (epg) than lambs that had grazed on pastures, which had not carried sheep the previous year. This beneficial effect of lambs grazing non-infected pastures persisted if the ewes were treated with an anthelmintic before turn-out and if the lambs were kept on pastures of low infectivity after weaning. In lambs, the prevalence and the magnitude of their egg counts were higher during autumn in flocks where lambs were slaughtered after 8 months of age, compared with flocks where all lambs were slaughtered before this age. These results will be used in providing advice to farmers of ways to modify their flock management in order to minimise the use of anthelmintics, but at the same time efficiently produce prime lambs
The state space and physical interpretation of self-similar spherically symmetric perfect-fluid models
The purpose of this paper is to further investigate the solution space of
self-similar spherically symmetric perfect-fluid models and gain deeper
understanding of the physical aspects of these solutions. We achieve this by
combining the state space description of the homothetic approach with the use
of the physically interesting quantities arising in the comoving approach. We
focus on three types of models. First, we consider models that are natural
inhomogeneous generalizations of the Friedmann Universe; such models are
asymptotically Friedmann in their past and evolve fluctuations in the energy
density at later times. Second, we consider so-called quasi-static models. This
class includes models that undergo self-similar gravitational collapse and is
important for studying the formation of naked singularities. If naked
singularities do form, they have profound implications for the predictability
of general relativity as a theory. Third, we consider a new class of
asymptotically Minkowski self-similar spacetimes, emphasizing that some of them
are associated with the self-similar solutions associated with the critical
behaviour observed in recent gravitational collapse calculations.Comment: 24 pages, 12 figure
Designing isotropic interactions for self-assembly of complex lattices
We present a direct method for solving the inverse problem of designing
isotropic potentials that cause self-assembly into target lattices. Each
potential is constructed by matching its energy spectrum to the reciprocal
representation of the lattice to guarantee that the desired structure is a
ground state. We use the method to self-assemble complex lattices not
previously achieved with isotropic potentials, such as a snub square tiling and
the kagome lattice. The latter is especially interesting because it provides
the crucial geometric frustration in several proposed spin liquids.Comment: 4 pages, 3 figure
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