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Nathalie Deruelle
Nathalie Deruelle (born 1952) is a French physicist specializing in general relativity and known for her research on the two-body problem in general relativity and on cosmological perturbation theory. Education and career Deruelle began her studies at the École normale supérieure in 1971, earned an agrégation in 1975, then, after visiting positions at the European Space Agency and the University of Cambridge, completed a doctorate in 1982 at Pierre and Marie Curie University. Formerly a director of research for the French National Centre for Scientific Research, associated with Paris Diderot University, she is now listed as a researcher emeritus. Books Deruelle is the author of books including: *''Relativity in Modern Physics'' (with Jean-Philippe Uzan, 2018) *''Les ondes gravitationnelles'' (with Jean-Pierre Lasota, 2018) *''De Pythagore à Einstein, tout est nombre : la relativité générale, 25 siècles d'histoire'' (2015) *''Théories de la relativité'' (with Jean-Philip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the ' is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations. Newton's law of universal gravitation, which describes classical gravity, can be seen as a prediction of general relativity for the almost flat spacetime geometry around stationary mass distributions. Some predictions of general relativity, however, are beyond Newton's law of universal gravitat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-body Problem In General Relativity
The two-body problem in general relativity is the determination of the motion and gravitational field of two bodies as described by the field equations of general relativity. Solving the Kepler problem is essential to calculate the bending of light by gravity and the motion of a planet orbiting its sun. Solutions are also used to describe the motion of binary stars around each other, and estimate their gradual loss of energy through gravitational radiation. General relativity describes the gravitational field by curved space-time; the field equations governing this curvature are nonlinear and therefore difficult to solve in a closed form. No exact solutions of the Kepler problem have been found, but an approximate solution has: the Schwarzschild solution. This solution pertains when the mass ''M'' of one body is overwhelmingly greater than the mass ''m'' of the other. If so, the larger mass may be taken as stationary and the sole contributor to the gravitational field. This is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmological Perturbation Theory
In physical cosmology, cosmological perturbation theory is the theory by which the ''evolution of structure'' is understood in the Big Bang model. It uses general relativity to compute the gravitational forces causing small perturbations to grow and eventually seed the formation of stars, quasars, galaxies and clusters. It only applies to situations in which the universe is predominantly homogeneous, such as during cosmic inflation and large parts of the Big Bang. The universe is believed to still be homogeneous enough that the theory is a good approximation on the largest scales, but on smaller scales more involved techniques, such as N-body simulations, must be used. Because of the gauge invariance of general relativity, the correct formulation of cosmological perturbation theory is subtle. In particular, when describing an inhomogeneous spacetime there is often not a preferred coordinate choice. There are currently two distinct approaches to perturbation theory in classical gener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
École Normale Supérieure (Paris)
The ''École normale supérieure - PSL'' (; also known as ''ENS'', ''Normale sup, ''Ulm'' or ''ENS Paris'') is a ''grande école'' university in Paris, France. It is one of the constituent members of Paris Sciences et Lettres University (PSL). Originally conceived during the French Revolution, the school was founded in 1794 to provide homogeneous training of high-school teachers in France but it later closed. The school was subsequently reestablished by Napoleon I as ''pensionnat normal'' from 1808 to 1822, before being recreated in 1826 and taking the name of ''École normale'' in 1830. When institutes for primary teachers training called é''coles normales'' were created in 1845, the word ''supérieure'' (meaning upper) was added to form the current name. It has since developed into an institution which has become a platform for French students to pursue careers in government and academia. The ENS has a highly competitive selection process consisting of written and oral exami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agrégation
In France, the ''agrégation'' () is a competitive examination for civil service in the French public education system. Candidates for the examination, or ''agrégatifs'', become ''agrégés'' once they are admitted to the position of ''professeur agrégé''. In France, ''professeurs agrégés'' are distinguished from ''professeurs certifiés'' recruited through the CAPES training. The ''agrégés'' are usually expected to teach in sixth-form colleges (''lycées'') and universities, while the ''certifiés'' usually teach in secondary schools (''collèges''), although there is a significant overlap. The examination may require more than a year of preparation. The difficulty and selectivity (quota) vary from one discipline to another: there are about 300 such positions open each year for mathematics alone, but usually fewer positions are made available for humanities and social sciences (for example, 61 positions for philosophy were offered in 2018) and perhaps only one seat in som ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Space Agency
, owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (12052189474).jpg , size = , caption = , acronym = , established = , employees = 2,200 , administrator = Director General Josef Aschbacher , budget = €7.2 billion (2022) , language = English and French (working languages) , website = , logo = European Space Agency logo.svg , logo_caption = Logo , image_caption = European Space Operations Centre (ESOC) Main Control Room The European Space Agency (ESA; french: Agence spatiale européenne , it, Agenzia Spaziale Europea, es, Agencia Espacial Europea ASE; german: Europäische Weltraumorganisation) is an intergovernmental organisation of 22 member states dedicated to the exploration of space. Established in 1975 and headquartered i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
