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Eugene Wigner
Eugene Paul "E. P." Wigner ( hu, Wigner Jenő Pál, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles". A graduate of the Technical University of Berlin, Wigner worked as an assistant to Karl Weissenberg and Richard Becker at the Kaiser Wilhelm Institute in Berlin, and David Hilbert at the University of Göttingen. Wigner and Hermann Weyl were responsible for introducing group theory into physics, particularly the theory of symmetry in physics. Along the way he performed ground-breaking work in pure mathematics, in which he authored a number of mathematical theorems. In particular, Wigner's theorem is a cornerstone in the mathematical formulation of quantum mechanics. He is also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Budapest
Budapest (, ; ) is the capital and most populous city of Hungary. It is the ninth-largest city in the European Union by population within city limits and the second-largest city on the Danube river; the city has an estimated population of 1,752,286 over a land area of about . Budapest, which is both a city and county, forms the centre of the Budapest metropolitan area, which has an area of and a population of 3,303,786; it is a primate city, constituting 33% of the population of Hungary. The history of Budapest began when an early Celtic settlement transformed into the Roman town of Aquincum, the capital of Lower Pannonia. The Hungarians arrived in the territory in the late 9th century, but the area was pillaged by the Mongols in 1241–42. Re-established Buda became one of the centres of Renaissance humanist culture by the 15th century. The Battle of Mohács, in 1526, was followed by nearly 150 years of Ottoman rule. After the reconquest of Buda in 1686, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Victor Frederick Weisskopf
Victor Frederick "Viki" Weisskopf (also spelled Viktor; September 19, 1908 – April 22, 2002) was an Austrian-born American theoretical physicist. He did postdoctoral work with Werner Heisenberg, Erwin Schrödinger, Wolfgang Pauli, and Niels Bohr. During World War II he was Group Leader of the Theoretical Division of the Manhattan Project at Los Alamos, and he later campaigned against the proliferation of nuclear weapons. Biography Weisskopf was born in Vienna to Jewish parents and earned his doctorate in physics at the University of Göttingen in Germany in 1931. His brilliance in physics led to work with the great physicists exploring the atom, especially Niels Bohr, who mentored Weisskopf at his institute in Copenhagen. By the late 1930s, he realized that, as a Jew, he needed to get out of Europe. Bohr helped him find a position in the United States. In the 1930s and 1940s, "Viki", as everyone called him, made major contributions to the development of quantum theory, esp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wigner's Friend
Wigner's friend is a thought experiment in theoretical quantum physics, first conceived by the physicist Eugene Wigner in 1961, Reprinted in and further developed by David Deutsch in 1985. The scenario involves an indirect observation of a quantum measurement: An observer W observes another observer F who performs a quantum measurement on a physical system. The two observers then formulate a statement about the physical system's state after the measurement according to the laws of quantum theory. However, in most of the interpretations of quantum mechanics, the resulting statements of the two observers contradict each other. This reflects a seeming incompatibility of two laws in quantum theory: the deterministic and continuous time evolution of the state of a closed system and the nondeterministic, discontinuous collapse of the state of a system upon measurement. Wigner's friend is therefore directly linked to the measurement problem in quantum mechanics with its famous Schrödinger ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wigner–Eckart Theorem
The Wigner–Eckart theorem is a theorem of representation theory and quantum mechanics. It states that matrix elements of spherical tensor operators in the basis of angular momentum eigenstates can be expressed as the product of two factors, one of which is independent of angular momentum orientation, and the other a Clebsch–Gordan coefficient. The name derives from physicists Eugene Wigner and Carl Eckart, who developed the formalism as a link between the symmetry transformation groups of space (applied to the Schrödinger equations) and the laws of conservation of energy, momentum, and angular momentum.Eckart Biography – The National Academies Press. Mathematically, the Wigner–Eckart theorem is generally stated in the following way. Given a tensor operator and two states of angular mome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wigner D-matrix
The Wigner D-matrix is a unitary matrix in an irreducible representation of the groups SU(2) and SO(3). It was introduced in 1927 by Eugene Wigner, and plays a fundamental role in the quantum mechanical theory of angular momentum. The complex conjugate of the D-matrix is an eigenfunction of the Hamiltonian of spherical and symmetric rigid rotors. The letter stands for ''Darstellung'', which means "representation" in German. Definition of the Wigner D-matrix Let be generators of the Lie algebra of SU(2) and SO(3). In quantum mechanics, these three operators are the components of a vector operator known as ''angular momentum''. Examples are the angular momentum of an electron in an atom, electronic spin, and the angular momentum of a rigid rotor. In all cases, the three operators satisfy the following commutation relations, : _x,J_y= i J_z,\quad _z,J_x= i J_y,\quad _y,J_z= i J_x, where ''i'' is the purely imaginary number and Planck's constant has been set equal to one. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parity (physics)
In physics, a parity transformation (also called parity inversion) is the flip in the sign of ''one'' spatial coordinate. In three dimensions, it can also refer to the simultaneous flip in the sign of all three spatial coordinates (a point reflection): :\mathbf: \beginx\\y\\z\end \mapsto \begin-x\\-y\\-z\end. It can also be thought of as a test for chirality of a physical phenomenon, in that a parity inversion transforms a phenomenon into its mirror image. All fundamental interactions of elementary particles, with the exception of the weak interaction, are symmetric under parity. The weak interaction is chiral and thus provides a means for probing chirality in physics. In interactions that are symmetric under parity, such as electromagnetism in atomic and molecular physics, parity serves as a powerful controlling principle underlying quantum transitions. A matrix representation of P (in any number of dimensions) has determinant equal to −1, and hence is distinct from a rotat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conservation Law (physics)
In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves over time. Exact conservation laws include conservation of energy, conservation of linear momentum, conservation of angular momentum, and conservation of electric charge. There are also many approximate conservation laws, which apply to such quantities as mass, parity, lepton number, baryon number, strangeness, hypercharge, etc. These quantities are conserved in certain classes of physics processes, but not in all. A local conservation law is usually expressed mathematically as a continuity equation, a partial differential equation which gives a relation between the amount of the quantity and the "transport" of that quantity. It states that the amount of the conserved quantity at a point or within a volume can only change by the amount of the quantity which flows in or out of the volume. From Noether's theorem, each conservation law is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bargmann–Wigner Equations
:''This article uses the Einstein summation convention for tensor/spinor indices, and uses hats for quantum operators. In relativistic quantum mechanics and quantum field theory, the Bargmann–Wigner equations describe free particles with non-zero mass and arbitrary spin , an integer for bosons () or half-integer for fermions (). The solutions to the equations are wavefunctions, mathematically in the form of multi-component spinor fields. They are named after Valentine Bargmann and Eugene Wigner. History Paul Dirac first published the Dirac equation in 1928, and later (1936) extended it to particles of any half-integer spin before Fierz and Pauli subsequently found the same equations in 1939, and about a decade before Bargman, and Wigner. Eugene Wigner wrote a paper in 1937 about unitary representations of the inhomogeneous Lorentz group, or the Poincaré group. Wigner notes Ettore Majorana and Dirac used infinitesimal operators applied to functions. Wigner classifies repres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joseph O
Joseph is a common male given name, derived from the Hebrew Yosef (יוֹסֵף). "Joseph" is used, along with "Josef", mostly in English, French and partially German languages. This spelling is also found as a variant in the languages of the modern-day Nordic countries. In Portuguese and Spanish, the name is "José". In Arabic, including in the Quran, the name is spelled '' Yūsuf''. In Persian, the name is "Yousef". The name has enjoyed significant popularity in its many forms in numerous countries, and ''Joseph'' was one of the two names, along with ''Robert'', to have remained in the top 10 boys' names list in the US from 1925 to 1972. It is especially common in contemporary Israel, as either "Yossi" or "Yossef", and in Italy, where the name "Giuseppe" was the most common male name in the 20th century. In the first century CE, Joseph was the second most popular male name for Palestine Jews. In the Book of Genesis Joseph is Jacob's eleventh son and Rachel's first son, and k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fred Tappert
Frederick Drach Tappert (April 21, 1940 – January 9, 2002) was an American physicist whose primary contributions were in underwater acoustics. He is noted for the development of the parabolic equation model and split-step Fourier algorithm for electromagnetic and ocean acoustic propagation. Fred Tappert was born in April 1940 to Rev. Dr. Theodore Gerhardt Tappert and Helen Carson Tappert. As a child, Fred lived with his family on the campus of the Lutheran Theological Seminary in the Germantown neighborhood of Northwest Philadelphia. He attended Central High School in Philadelphia and Pennsylvania State University. Growing up, his father "often mentioned the satisfaction that would result from the pursuit of knowledge for its own sake." Tappert began his scientific career in the field of plasma physics, receiving his Ph.D. from Princeton University in 1967. His dissertation, entitled "Kinetic theory of equilibrium plasmas", was supervised by Edward A. Frieman, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conyers Herring
William Conyers Herring (November 15, 1914 – July 23, 2009) was an American physicist. He was a Professor of Applied Physics at Stanford University and the Wolf Prize in Physics recipient in 1984/5. Academic career Conyers Herring completed his Ph.D. in physics from Princeton University in 1937, submitting a dissertation entitled ''On Energy Coincidences in the Theory of Brillouin Zones'' under the direction of Eugene Wigner. In 1946, he joined the technical staff of Bell Laboratories in Murray Hill, New Jersey, where he remained until 1978. Then, he joined the faculty at Stanford University. Contributions Conyers Herring played a major role in the development of solid state physics. He laid the foundations of band structure calculations of metals and semiconductors, culminating in the discovery of the Orthogonalized Plane Wave Method (O.P.W.) in 1940. He was years ahead of his time in this contribution. A great deal of modern solid state physics as produced today stems from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frederick Seitz
Frederick Seitz (July 4, 1911 – March 2, 2008) was an American physicist and a pioneer of solid state physics and lobbyist. Seitz was the 4th president of Rockefeller University from 1968–1978, and the 17th president of the United States National Academy of Sciences from 1962–1969. Seitz was the recipient of the National Medal of Science, NASA's Distinguished Public Service Award, and other honors. He founded the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana–Champaign and several other material research laboratories across the United States. Seitz was also the founding chairman of the George C. Marshall Institute, a tobacco industry consultant, and a prominent climate change denier. Background and personal life Born in San Francisco on July 4, 1911, Seitz graduated from Lick-Wilmerding High School in the middle of his senior year, and went on to study physics at Stanford University obtaining his bachelor's degree in three years, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
