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Louis Michel (physicist)
Louis Michel (1923–1999) was a French mathematical physicist at the Institut des Hautes Études Scientifiques (IHÉS). He was born in Roanne, in the Loire department in central France, on 4 May 1923, and died in Bures-sur-Yvette (Essonne), in the Île-de-France region, on 30 December 1999. Biography Michel completed his studies at the École Polytechnique in Paris. After World War II, he went to Manchester, England, where he worked on weak interactions. Back in France, he was teaching in Lille and Orsay before creating the ''Centre de Physique Théorique of the École Polytechnique'' (CPHT) in Palaiseau. In 1962, he became a permanent professor at ''Institut des Hautes Études Scientifiques'' (IHÉS) in Bures-sur-Yvette, where he remained until his retirement, and as an emeritus professor until his death. Louis Michel was President of the Société Française de Physique between 1978 and 1980, and a member of the French Academy of Sciences since 1979. In 1982, he was awarded the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Institut Des Hautes Études Scientifiques
The Institut des hautes études scientifiques (IHÉS; English: Institute of Advanced Scientific Studies) is a French research institute supporting advanced research in mathematics and theoretical physics. It is located in Bures-sur-Yvette, just south of Paris. It is an independent research institute in a partnership with the University of Paris-Saclay. History The IHÉS was founded in 1958 by businessman and mathematical physicist Léon Motchane with the help of Robert Oppenheimer and Jean Dieudonné as a research centre in France, modeled on the renowned Institute for Advanced Study in Princeton, United States. The strong personality of Alexander Grothendieck and the broad sweep of his revolutionizing theories were a dominating feature of the first ten years at the IHÉS. René Thom received an invitation from IHÉS in 1963 and after his appointment remained there until his death in 2002. Dennis Sullivan is remembered as one who had a special talent for encouraging fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
École Polytechnique (France)
École polytechnique, also known as Polytechnique or l'X , is a ''grande école'' university located in Palaiseau, France. It specializes in science and engineering and is a founding member of the Polytechnic Institute of Paris. The school was founded in 1794 by mathematician Gaspard Monge during the French Revolution and was militarized under Napoleon I in 1804. It is still supervised by the French Ministry of Armed Forces. Originally located in the Latin Quarter in central Paris, the institution moved to Palaiseau in 1976, in the Paris-Saclay technology cluster. Polytechnique’s historic engineering graduate program has a highly selective admission process consisting of written and oral examinations, following ''classes préparatoires'' or a bachelor’s degree. French engineering students undergo initial military training and have the status of paid officer cadets. The school has also been awarding doctorates since 1985, masters since 2005 and bachelors since 2017. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spin (physics)
Spin is a conserved quantity carried by elementary particles, and thus by composite particles ( hadrons) and atomic nuclei. Spin is one of two types of angular momentum in quantum mechanics, the other being ''orbital angular momentum''. The orbital angular momentum operator is the quantum-mechanical counterpart to the classical angular momentum of orbital revolution and appears when there is periodic structure to its wavefunction as the angle varies. For photons, spin is the quantum-mechanical counterpart of the polarization of light; for electrons, the spin has no classical counterpart. The existence of electron spin angular momentum is inferred from experiments, such as the Stern–Gerlach experiment, in which silver atoms were observed to possess two possible discrete angular momenta despite having no orbital angular momentum. The existence of the electron spin can also be inferred theoretically from the spin–statistics theorem and from the Pauli exclusion principle— ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bargmann–Michel–Telegdi Equation
In physics, Larmor precession (named after Joseph Larmor) is the precession of the magnetic moment of an object about an external magnetic field. The phenomenon is conceptually similar to the precession of a tilted classical gyroscope in an external torque-exerting gravitational field. Objects with a magnetic moment also have angular momentum and effective internal electric current proportional to their angular momentum; these include electrons, protons, other fermions, many atomic and nuclear systems, as well as classical macroscopic systems. The external magnetic field exerts a torque on the magnetic moment, :\vec = \vec\times\vec = \gamma\vec\times\vec, where \vec is the torque, \vec is the magnetic dipole moment, \vec is the angular momentum vector, \vec is the external magnetic field, \times symbolizes the cross product, and \gamma is the gyromagnetic ratio which gives the proportionality constant between the magnetic moment and the angular momentum. The angular momentum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michel Parameters
The Michel parameters, usually denoted by \rho, \eta, \xi and \delta, are four parameters used in describing the phase space distribution of leptonic decays of charged leptons, l_^-\rightarrow l_^\nu_\bar. They are named after the physicist Louis Michel. Sometimes instead of \delta, the product \xi\delta is quoted. Within the Standard Model of electroweak interactions, these parameters are expected to be : \rho=, \quad \eta=0, \quad \xi=1, \quad \xi\delta=. Precise measurements of energy and angular distributions of the daughter leptons in decays of polarized muons and tau leptons are so far in good agreement with these predictions of the Standard Model. Muon decay Consider the decay of the positive muon: :\mu^+\to e^+ + \nu_e + \bar\nu_\mu. In the muon rest frame, energy and angular distributions of the positrons emitted in the decay of a polarised muon expressed in terms of Michel parameters are the following, neglecting electron and neutrino masses and the radiative corrections ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spontaneous Symmetry Breaking
Spontaneous symmetry breaking is a spontaneous process of symmetry breaking, by which a physical system in a symmetric state spontaneously ends up in an asymmetric state. In particular, it can describe systems where the equations of motion or the Lagrangian obey symmetries, but the lowest-energy vacuum solutions do not exhibit that same symmetry. When the system goes to one of those vacuum solutions, the symmetry is broken for perturbations around that vacuum even though the entire Lagrangian retains that symmetry. Overview By definition, spontaneous symmetry breaking requires the existence of physical laws (e.g. quantum mechanics) which are invariant under a symmetry transformation (such as translation or rotation), so that any pair of outcomes differing only by that transformation have the same probability distribution. For example if measurements of an observable at any two different positions have the same probability distribution, the observable has translational symm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word ''crystal'' derives from the Ancient Greek word (), meaning both " ice" and " rock crystal", from (), "icy cold, frost". Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most metals, rocks, ceramics, and ice. A third ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three generations of fermions, but ordinary matter is made only from the first fermion generation. The first generation consists of up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quarks cannot exist on their own but form hadrons. Hadrons that contain an odd number of quarks are called baryons and those that contain an even number are called mesons. Two baryons, the proton and the neutron, make up most of the mass of ordinary matter. Mesons are unstable and the longest-lived last for only a few hundre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elementary Particle
In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions (quarks, leptons, antiquarks, and antileptons, which generally are matter particles and antimatter particles), as well as the fundamental bosons ( gauge bosons and the Higgs boson), which generally are force particles that mediate interactions among fermions. A particle containing two or more elementary particles is a composite particle. Ordinary matter is composed of atoms, once presumed to be elementary particles – ''atomos'' meaning "unable to be cut" in Greek – although the atom's existence remained controversial until about 1905, as some leading physicists regarded molecules as mathematical illusions, and matter as ultimately composed of energy. Subatomic constituents of the atom were first identified in the early 1930s; the electron and the proton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theoretical Physics
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experimental tools to probe these phenomena. The advancement of science generally depends on the interplay between experimental studies and theory. In some cases, theoretical physics adheres to standards of mathematical rigour while giving little weight to experiments and observations.There is some debate as to whether or not theoretical physics uses mathematics to build intuition and illustrativeness to extract physical insight (especially when normal experience fails), rather than as a tool in formalizing theories. This links to the question of it using mathematics in a less formally rigorous, and more intuitive or heuristic way than, say, mathematical physics. For example, while developing special relativity, Albert Einstein was concer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wigner Medal
The International Colloquium on Group Theoretical Methods in Physics is an academic conference devoted to applications of group theory to physics. It was founded in 1972 by Henri Bacry and Aloysio Janner. It hosts a colloquium every two years. The ICGTMP is led by a standing committee, which helps select winners for the two major awards presented at the conference: the Wigner Medal and the Weyl Prize. Wigner Medal The Wigner Medal is an award designed "to recognize outstanding contributions to the understanding of physics through Group Theory". The Wigner Medal is administered by The Group Theory and Fundamental Physics Foundation, a publicly supported organization. Donations are tax-deductible as provided pursuant to the provisions of Section 170 of the Internal Revenue Code, a federal code of the United States. The award was first presented in 1978 to Eugene Wigner, and was first awarded at the Integrative Conference on Group Theory and Mathematical Physics. List of conferen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
French Academy Of Sciences
The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at the forefront of scientific developments in Europe in the 17th and 18th centuries, and is one of the earliest Academies of Sciences. Currently headed by Patrick Flandrin (President of the Academy), it is one of the five Academies of the Institut de France. History The Academy of Sciences traces its origin to Colbert's plan to create a general academy. He chose a small group of scholars who met on 22 December 1666 in the King's library, near the present-day Bibliothèque Nationals, and thereafter held twice-weekly working meetings there in the two rooms assigned to the group. The first 30 years of the Academy's existence were relatively informal, since no statutes had as yet been laid down for the institution. In contrast to its Brit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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