Théorie des Cordes : Ce qu'Einstein ne Savait pas Encore (FR) - Version longue Recent Physics of the Dark Universe Articles Recently published articles from Physics of the Dark Universe. EURECA Conceptual Design Report The EURECA Collaboration Available online 4 April 2014G. Angloher | E. Armengaud | C. The EURECA (European Underground Rare Event Calorimeter Array) project is aimed at searching for dark matter particles using cryogenic bolometers. Cold dark matter halos in Multi-coupled Dark Energy cosmologies: Structural and statistical properties April 2014Marco Baldi The recently proposed Multi-coupled Dark Energy (McDE) scenario – characterised by two distinct cold dark matter (CDM) particle species with opposite couplings to a Dark Energy scalar field – introduces... Virtual gravitational dipoles: The key for the understanding of the Universe? April 2014Dragan Slavkov Hajdukovic Before the end of this decade, three competing experiments (ALPHA, AEGIS and GBAR) will discover if atoms of antihydrogen fall up or down. A way forward for Cosmic Shear: Monte-Carlo Control Loops December 2013Maya Lincoln | Avi Wasser
Bulletproof Skin Made From Spider Silk Just last week we learned about spiders coming to the aid of burn victims. Now it looks like our friendly neighborhood arachnids are being used to create the ultimate superhero power: bulletproof human skin. Well, almost. BLOG: Artificial Skin Made From Spider Silk In her new project, 2.6g 329m/s, Dutch artist Jalila Essaidi, along with Forensic Genomics Consortium Netherlands, created a swatch of nearly bulletproof skin made from spider silk and human skin cells. By grafting spider silk between the epidermis and dermis, the skin was able to stop a bullet that was fired at a reduced speed. But that's fine with Essaidi. "With this work I want to show that safety in its broadest sense is a relative concept, and hence the term bulletproof," Essaidi said in a press release. "But even with the skin pierced by the bullet the experiment is still a success. NEWS: How To Make A Bulletproof T-Shirt [Via TechNewsDaily] photo: A bullet is repelled by a matrix of spider silk and human skin cells.
Physics and Physicists Équation de Dirac Un article de Wikipédia, l'encyclopédie libre. L'équation de Dirac est une équation formulée par Paul Dirac en 1928 dans le cadre de sa mécanique quantique relativiste de l'électron. Il s'agit au départ d'une tentative pour incorporer la relativité restreinte à des modèles quantiques, avec une écriture linéaire entre la masse et l'impulsion. Explication[modifier | modifier le code] Cette équation décrit le comportement de particules élémentaires de spins demi-entiers, comme les électrons. Cette équation prend en compte de manière naturelle la notion de spin introduite peu de temps avant et permit de prédire l'existence des antiparticules. Il est par ailleurs notable que l'opérateur de Dirac, découvert pour des raisons absolument physiques (et théoriques), aura en mathématiques un grand avenir par son usage indispensable dans l'un des plus profonds résultats du siècle, le théorème de l'indice démontré dans les années 1960. Formulation mathématique[modifier | modifier le code] et
Backreaction The Mathematics of Lego | Wired Science The world of toys and games is not immune to mathematics. From the Rubik’s Cube to Monopoly, fun pastimes can be quantified. And the same is true of Legos. To see that, we have to begin thinking about how we combine things together. In the wonderfully titled paper Scaling of Differentiation in Networks: Nervous Systems, Organisms, Ant Colonies, Ecosystems, Businesses, Universities, Cities, Electronic Circuits, and Legos, Mark Changizi and his colleagues set out to understand this concept. And this includes, of course, Lego bricks. They found that the number of piece types to total number of pieces could be fit nicely to a power law. This curve demonstrates that as the number of pieces in a set grows, so do the number of piece types. I have seen other research that uses Lego pieces as building blocks, but this is the first study I have come across that actually examines pre-existing Lego sets as systems themselves. Top image:enerva/Flickr/CC-licensed
Preposterous Universe Usually, technical advances in mathematical physics don’t generate a lot of news buzz. But last year a story in Quanta proved to be an exception. It relayed the news of an intriguing new way to think about quantum field theory — a mysterious mathematical object called the Amplituhedron, which gives a novel perspective on how we think about the interactions of quantum fields. This is cutting-edge stuff at the forefront of modern physics, and it’s not an easy subject to grasp. “Halfway between a popular account and a research paper” can still be pretty forbidding for the non-experts, but hopefully this guest blog post will convey some of the techniques used and the reasons why physicists are so excited by these (still very tentative) advances. I would like to thank Sean to give me an opportunity to write about my work on his blog. represented by a single Feynman diagram. As a first step, we need to characterize how the amplitude is invariantly defined in a traditional way.
conférence de Strominger (2012): Black holes: harmonic oscillators of the 21st century I think that my ex-colleague Andy Strominger is not only a top physicist but also a captivating speaker. This talk he gave at Berkeley in March 2012 confirms it. Abstract is here... Click the picture above to try to play the MOV video. You may need to install QuickTime/iTunes if it doesn't work for you. After a minute spent with a different colloquium at the following week (whose title was in Latin), Andy Strominger quickly jumps to his main point. In the early 21st century, black holes seem to play the same universal exploratory role in physics that the quantum harmonic oscillator used to play almost 100 years earlier. It sounds almost like poetry but it's actually true although one needs to appreciate many aspects of black holes that general relativity, its semiclassical quantization, and later string theory discovered to appreciate the depth of the summary above. Andy has a certain time to communicate these insights. Rapid progress came in the 1970s. Questions and answers
The Reference Frame les leçons de la mécanique quantique-formalisme quantique Mioara Mugur-Schächter * Note. Le texte qui suit est le manuscrit d'un article envoyé à la revue Le Débat. L'objectif de ce texte était de communiquer à un public plus large un constat et un but qui ont pu fédérer quelques chercheurs de compétences différentes pour constituer ensemble un Centre pour la Synthèse d'une Épistémologie Formalisée (CeSEF) qui travaille depuis 1994. Sur les frontières de la pensée on peut discerner des formes nouvelles. Chez les mathématiciens s'est établie la notion que les possibilités de principe des actions mathématiques ont des limites (la cohérence formelle d'une assertion mathématique, avec les données explicites qui définissent le système formel où cette assertion est formulée, n'est pas toujours décidable à l'intérieur de ce système, etc.). Les frontières entre le système étudié et le reste, son environnement, s'esquivent. Dès qu'il s'agit du vivant l'artificiel dans la distinction entre cause et but devient frappant. Bref :
RÉSONAANCES Le dilaton for Theorie des Cordes Théorie des Supercordes 02/08/2004 1. Introduction Le but de cette étude est d'expliquer l'historique de l'élaboration de la théorie des cordes.A cette occasion, nous présenterons, bien sûr, le contexte dans lequel cette gestation a eu lieu. Nousserons donc amenés à parler des autres théories physiques fondamentales. Celles-ci serontexpliquées dans les grandes lignes en mettant l'accent sur les aspects intéressants pour la théoriedes cordes.Je n'aborderai pas les aspects expérimentaux, c'est à dire les expériences actuelles ou futures quipourraient confirmer ou infirmer la théorie des cordes ou départager plusieurs de ses variantes. © Alexandre Depire 3/136
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