Refine
Year of publication
- 2013 (1053) (remove)
Document Type
- Article (1053) (remove)
Is part of the Bibliography
- yes (1053) (remove)
Keywords
- Climate change (6)
- gamma rays: galaxies (6)
- Eye movements (5)
- climate change (5)
- galaxies: active (5)
- Arabidopsis thaliana (4)
- Children (4)
- Development (4)
- Land use change (4)
- Reading (4)
Institute
- Institut für Biochemie und Biologie (182)
- Institut für Physik und Astronomie (152)
- Institut für Geowissenschaften (140)
- Institut für Chemie (99)
- Department Psychologie (63)
- Institut für Romanistik (48)
- Department Linguistik (39)
- Institut für Mathematik (36)
- Institut für Germanistik (30)
- Sozialwissenschaften (27)
In this paper we give some general considerations about circularly symmetric, static space-times in 2+1 dimensions, focusing first on the surprising (at the time) existence of the BTZ black hole solution. We show that BTZ black holes and Schwarzschild black holes in 3+1 dimensions originate from different definitions of a black hole. There are two by-products of this general discussion: (i) we give a new and simple derivation of 2+1 dimensional Anti-de Sitter (AdS) space-time; (ii) we present an exact solution to 2+1 dimensional gravity coupled to a self-interacting real scalar field. The spatial part of the metric of this solution is flat but the temporal part behaves asymptotically like AdS space-time. The scalar field has logarithmic behavior as one would expect for a massless scalar field in flat space- time. The solution can be compared to gravitating scalar field solutions in 3+1 dimensions but with certain oddities connected with the 2+1 dimensional character of the space-time. The solution is unique to 2+1 dimensions; it does not carry over to 3+1 dimensions.
We study a broad class of isotropic vacuum cosmologies in fourth-order gravity under the condition that the gravitational Lagrangian be scale-invariant or almost scale-invariant. The gravitational Lagrangians considered will be of the form L = f(R) + k(G) where R and G are the Ricci and Gauss-Bonnet scalars respectively. Specifically we take f(R) = R^2n and k(G) = G^n or k(G) = G ln G. We find solutions in closed form for a spatially flat Friedmann space-time and interpret their asymptotic early-time and late-time behaviour as well as their inflationary stages. One unique example which we discuss is the case of a very small negative value of the parameter b in the Lagrangian L = R^2 + b G ln G which leads to the replacement of the exact de Sitter solution from L = R^2 (being a local attractor) to a power-law inflation exact solution also representing a local attractor. This shows how one can modify the dynamics from de Sitter to power-law inflation by the addition of the G ln G-term.
We classify the existent Birkhoff-type theorems into four classes: First, in field theory, the theorem states the absence of helicity 0- and spin 0-parts of the gravitational field. Second, in relativistic astrophysics, it is the statement that the gravitational far-field of a spherically symmetric star carries, apart from its mass, no information about the star; therefore, a radially oscillating star has a static gravitational far-field. Third, in mathematical physics, Birkhoff's theorem reads: up to singular exceptions of measure zero, the spherically symmetric solutions of Einstein's vacuum field equation with Lambda = 0 can be expressed by the Schwarzschild metric; for Lambda unequal 0, it is the Schwarzschild-de Sitter metric instead. Fourth, in differential geometry, any statement of the type: every member of a family of pseudo-Riemannian space-times has more isometries than expected from the original metric ansatz, carries the name Birkhoff-type theorem. Within the fourth of these classes we present some new results with further values of dimension and signature of the related spaces; including them are some counterexamples: families of space-times where no Birkhoff-type theorem is valid. These counterexamples further confirm the conjecture, that the Birkhoff-type theorems have their origin in the property, that the two eigenvalues of the Ricci tensor of two- dimensional pseudo-Riemannian spaces always coincide, a property not having an analogy in higher dimensions. Hence, Birkhoff-type theorems exist only for those physical situations which are reducible to two dimensions.
Body composition
(2013)
Miedo y catástrofe : miedo ante la catástrofe ; sobre la economía del miedo de cara a la muerte
(2013)
Fußball als Text : Überlegungen zu den Weltmeisterschaften, Costa Rica und den Kulturwissenschaften
(2013)
Marguerite de Valois
(2013)
Cette étude est consacrée au portrait de Marguerite de Valois, surnommée la Reine Margot. En essayant de reconstruire ce portrait, on rencontre la difficulté que Marguerite de Valois, comme personnage historique qui a eu une biographie réelle, est devenue un personnage "fictionalisé" et littéraire. Pour cela, il est indispensable que l'étude du portrait littéraire prenne pour point de départ le recours aux faits historiques. Il est évident que l'histoire ne nous présente que l'image incomplète d'un personnage historique et qu'il n'existe pas de biographie complète qui mérite ce nom. Les blancs laissent suffisamment de place aux mythes qui finissent par se détacher si profondément de la réalité que le portrait historique s'en trouve déformé et défiguré en un dispositif d'affects négatifs. Il est de notre propos de rendre sa dignité à Marguerite de Valois et de ne pas laisser une des femmes les plus remarquables du XVIe siècle se dégrader en simulacre. Cette contribution, en restant au plus près des sources historiques de l'époque, relève quelques faits positifs pour remodeler un portrait d'une femme supérieure avant la lettre qui avait les visées hautes dans tous les domaines. L'étude se comprend en tant qu'appel à la redécouverte d'un personnage historique au portrait brouillé et enfoui.
Heimatgefühl als Schlüssel?
(2013)
Chillen gestern
(2013)
Von wegen Kinderspiel
(2013)
Der Aufsatz rekonstruiert Daniel Heinsius’ Verachtung der Philologie, wie sie in seinen „Orationes” zum Ausdruck kommt. Die These lautet, dass diese Verachtung in Heinsius’ neuplatonischer Poetik mit ihrer Sakralisierung der Dichtung begründet ist. In seinem Kommentar zur aristotelischen „Poetik“, der „Constitutio tragoediae“, ordnet Heinsius das technische Wissen der aristotelischen „Poetik“ der neuplatonischen Inspirationstheorie unter. Dadurch transformiert er den traditionellen, historisch-philologischen Kommentar in eine neue Form des technischen Handbuchs, wie es die „Constitutio tragoediae“ darstellt.
In articolul cu titlul "Identități hibride în comunitatea imigranților români" sunt prezentate rezultate parțiale precum și anumite analize a citatelor vorbitorilor din proiectul meu de doctorat cu titlul Sprachkontakt, Migration und Variation: Die frankophone Integration von Rumänen in Paris nach 1989. Lingvistica migratoare observă mișcările migranților români după căderea cortinei de fier. Aceștia au fost nevoiți să suporte consecințele managementului eronat al sistemului comunist. Între 1989 și 2012 mii de români au pǎrǎsit țara. Începând de atunci numărul imigranților români în Paris a crescut în mod significant. Scopul acestei contribuții este ilustrarea identității sociale a comunității migrante. În centrul lucrării se află descrierea procesului cultural și integrării lingvistice prin observarea dezvoltării a noi identități hibride.
Inhalt: 1. Fragestellungen und State of the Art 1.1 Forschungsfragen 1.2 Über den Stand der Forschung 1.3 Opposition in autoritären Regimen – klassisch und aktuell 2. Analyseschritte 2.1 Opposition in politischen Systemen 2.2 Handlungsdimensionen der Opposition 2.3 Idealtypen der Opposition in autoritären Regimen 2.4 Fünf forschungsleitende Hypothesen 3. Literaturverzeichnis