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Astrophysique relativiste --- General relativity (Physics) --- Relativistics astrophysics --- Gravitation
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Black holes (Astronomy). --- Black holes (Astronomy). --- General relativity (Physics). --- General relativity (Physics). --- Gravitational waves. --- Gravitational waves. --- Gravity waves. --- Gravity waves. --- Newtonian fluids. --- Newtonian fluids. --- Perturbation (Mathematics). --- Perturbation (Mathematics). --- Stellar oscillations. --- Stellar oscillations.
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Relativity (Physics) --- Mechanics. --- Relativité (Physique) --- Mécanique --- Einstein, Albert, --- Relativite (Physique) --- Relativité (Physique) --- Mécanique --- General relativity (Physics) --- Mathematics
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Neutron stars are the smallest denses stars known, with densities some 1014 times that of the Earth. They rotate with periods of fractions of a second, and their magnetic fields drive intense interstellar dynamos, lighting up entire nebulae. This text discusses the physics of these extreme objects. It includes the needed background in classical general relativity in nuclear and particle physics.
Compact objects (Astronomy) --- General relativity (Physics) --- Compact objects (Astronomy). --- General relativity (Physics). --- Observations, Astronomical. --- Astronomy—Observations. --- Astrophysics. --- Nuclear physics. --- Astronomy, Observations and Techniques. --- Astrophysics and Astroparticles. --- Particle and Nuclear Physics. --- Atomic nuclei --- Atoms, Nuclei of --- Nucleus of the atom --- Physics --- Astronomical physics --- Astronomy --- Cosmic physics --- Astronomical observations --- Observations, Astronomical
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Einstein aimait à répéter que le plus incompréhensible dans l'univers est bien qu'il soit compréhensible. La chose est-elle si sûre ? La théorie quantique des champs et la théorie de la relativité générale d'Einstein sont à l'heure actuelle les deux théories les mieux vérifiées en physique : pourra-t-on les unifier en une théorie quantique de la gravité ? Celle-ci expliquerait toutes les singularités - les premières secondes de l'univers comme la physique de ces objets énigmatiques sont les trous noirs. Notre intelligence de l'univers ferait alors un pas de géant. Mais quantique et cosmos peuvent-ils même être combinés ? Pourquoi notre coin d'univers ressemble-t-il exactement à ce qu'avait annoncé Einstein, sans trace d'effets quantiques visibles ? Mais quels étranges processus quantiques sont à l'oeuvre dans l'évaporation des trous noirs et qu'advient-il alors de l'information que ceux-ci ont avalée - les types, propriétés et configurations des particules qui y sont tombées ? Pourquoi le temps est-il orienté vers l'avant et non pas vers l'arrière ? La différence entre le passé et le futur provient-elle des conditions aux limites de l'univers ? Sur ces questions cruciales de l'espace et du temps, qui manifestent les insuffisances des théories, deux des plus célèbres physiciens - Stephen W. Hawking et Roger Penrose - s'opposent dans un débat sans concession. Pour Hawking, la relativité générale ne peut tout simplement pas expliquer l'origine de l'univers : seule une théorie quantique de la gravité, conjuguée avec l'hypothèse de l'absence de bord, peut espérer rendre compte du peu de choses que nous observons de notre univers. Pour Penrose, à l'instar d'Einstein, la mécanique quantique n'est pas le mot de la fin, elle n'est d'ailleurs pas achevée. Il lui semble préférable de travailler non pas dans un espace-temps ordinaire mais dans un espace mathématique particulier, l'espace des twistors, susceptible d'accueillir à la fois la relativité générale et la théorie quantique. Toute théorie, argue Hawking qui se dit positiviste, doit simplement fournir des prédictions s'accordant aux données expérimentales. Une simple comparaison des prédictions et des expériences, objecte Penrose, qui se veut réaliste, ne suffit pas : la théorie physique doit expliquer la réalité. En écho aux fameux débats qui opposèrent Einstein et Bohr sur les bizarres implications de la théorie quantique, cet ouvrage à deux voix donne à ses lecteurs l'occasion unique d'assister, aux premières loges, à l'élaboration, par la physique du XXIe siècle, des grandes réponses aux énigmes sur lesquelles vient encore buter notre compréhension du cosmos.
Temps --- --Philosophie des sciences --- --Espace --- --Gravité --- --Théorie --- --Physique quantique --- --Temps --- --Cosmology. --- General relativity (Physics) --- Physics --- Singularities (Mathematics) --- Moment spaces. --- Quantum theory. --- Astrophysics. --- Relativité générale (physique) --- Philosophie et physique. --- Singularités (mathématiques) --- Espace-temps. --- Physique --- Espace et temps. --- Théorie quantique --- Astrophysique. --- Cosmologie. --- Philosophy. --- Philosophie. --- Philosophie des sciences --- Espace --- Gravité --- Théorie --- Physique quantique
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During the course of this century, gauge invariance has slowly emerged from being an incidental symmetry of electromagnetism to being a fundamental geometrical principle underlying the four known fundamental physical interactions. The development has been in two stages. In the first stage (1916-1956) the geometrical significance of gauge-invariance gradually came to be appreciated and the original abelian gauge-invariance of electromagnetism was generalized to non-abelian gauge invariance. In the second stage (1960-1975) it was found that, contrary to first appearances, the non-abelian gauge-theories provided exactly the framework that was needed to describe the nuclear interactions (both weak and strong) and thus provided a universal framework for describing all known fundamental interactions. In this work, Lochlainn O'Raifeartaigh describes the former phase. O'Raifeartaigh first illustrates how gravitational theory and quantum mechanics played crucial roles in the reassessment of gauge theory as a geometric principle and as a framework for describing both electromagnetism and gravitation. He then describes how the abelian electromagnetic gauge-theory was generalized to its present non-abelian form. The development is illustrated by including a selection of relevant articles, many of them appearing here for the first time in English, notably by Weyl, Schrodinger, Klein, and London in the pre-war years, and by Pauli, Shaw, Yang-Mills, and Utiyama after the war. The articles illustrate that the reassessment of gauge-theory, due in a large measure to Weyl, constituted a major philosophical as well as technical advance.
Quantum field theory. --- Gauge invariance. --- Gravitation. --- Field theory (Physics) --- Matter --- Physics --- Antigravity --- Centrifugal force --- Relativity (Physics) --- Gage invariance --- Gauge transformations --- Invariance, Gauge --- Electromagnetism --- Symmetry (Physics) --- Transformations (Mathematics) --- Relativistic quantum field theory --- Quantum theory --- Properties --- Angular momentum. --- Balmer spectrum. --- Cartan gravitation. --- Charge conjugation. --- Diffeomorphisms. --- Eulerian derivative. --- Fermi statistics. --- General Theory. --- General relativity. --- Hamiltonian. --- Instantons. --- Jacobi identity. --- Kazimierz conference. --- Lagrangian. --- Lorentz transformation. --- Magnetic dipoles. --- Maxwell equations. --- Meson-Nucleon Interaction. --- Neutron. --- Pauli's theory. --- Renormalization. --- Rigid group. --- Topology. --- Virial theorem. --- Yang-Mills theory. --- Zeeman effect. --- action-density. --- conservation of isotopic. --- constants. --- divergence. --- factor. --- integral. --- quanta.
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Physics has the reputation of being difficult to understand and remote from everyday life. Robert Ehrlich, however, has spent much of his career disproving these stereotypes. In the long-awaited sequel to Turning the World Inside Out and 175 Other Simple Physics Demonstrations, he provides a new collection of physics demonstrations and experiments that prove that physics can, in fact, be "made simple." Intentionally using "low tech" and inexpensive materials from everyday life, Why Toast Lands Jelly-Side Down makes key principles of physics surprisingly easy to understand. After laying out the basic principles of what constitutes a successful demonstration, Ehrlich provides more than 100 examples. Some of the more intriguing include: Terminal Velocity of Falling Coffee Filters; Spinning a Penny; Dropping Two Rolls of Toilet Paper; Avalanches in a Sand Pile; When to Add the Cream to Your Coffee; Deep Knee Bends on a Bathroom Scale; Recoil Force on a Bent Straw; Swinging Your Arms While Walking; Estimating the Net Force on a Moving Book; and, of course, Why Toast Lands Jelly-Side Down. The book begins with a practical introduction on how to design physics demonstrations. The benefits of designing one's own "demos" are numerous, but primary among them is an increased understanding of basic physics. For many people who teach the principles of physics, demonstrations seem dauntingly complex, filled with hard-to-find equipment and too many possibilities for failure. The demonstrations described in this book are exactly the opposite. Ehrlich describes them with characteristic candor: "You can fit many of them in your pocket, bring them to your class without any set-up required, and best of all, you need not fear that your demo will more likely illustrate Murphy's laws rather than Newton's." For anyone with even the slightest interest in physics, Why Toast Lands Jelly-Side Down is filled with learning opportunities. For everyone who is studying physics or teaching the subject at any level, from amateur scientists to professional teachers, it is an essential resource.
Physics --- Experiments. --- Atwood's machine. --- Kipnis, Nahun. --- Newton's first law. --- World Wide Web. --- accelerometer. --- boulder in a boat. --- candle oscillator. --- capillary action. --- cavitation. --- chain reaction. --- depth of field. --- drag force. --- exchange processes. --- expansion of universe. --- floaters. --- general relativity. --- greenhouse effect. --- hourglass, weight of. --- inertial forces. --- inverse lawn sprinkler. --- inverted pendulum. --- invisibility. --- ladder against a wall. --- length contraction. --- magnetic dipole. --- magnetic marbles. --- missing circular arc. --- negative pinhole image. --- negative pressure. --- overhead projector uses. --- pinhole imaging. --- psychic powers. --- radiometer. --- relativity of simultaneity. --- rotating waves. --- sand piles. --- shock waves. --- siphon. --- soap bubbles. --- spinning a penny. --- spiral density wave. --- tachyons. --- tensile strength of water. --- terminal velocity. --- time dilation. --- tippy tops. --- total internal reflection. --- unstable equilibrium. --- water lens. --- weight of air. --- worldlines.
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