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Topic: Quantum mechanics


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  Quantum mechanics - Wikipedia, the free encyclopedia
Quantum mechanics is a more fundamental theory than Newtonian mechanics and classical electromagnetism, in the sense that it provides accurate and precise descriptions for many phenomena that these "classical" theories simply cannot explain on the atomic and subatomic level.
In the formalism of quantum mechanics, the state of a system at a given time is described by a complex number wave functions (sometimes referred to as orbitals in the case of atomic electrons), and more generally, elements of a complex vector space.
Quantum electrodynamics is a quantum theory of electrons, positrons, and the electromagnetic field, and served as a role model for subsequent quantum field theories.
en.wikipedia.org /wiki/Quantum_mechanics   (5473 words)

  
 Quantum theory - Wikipedia, the free encyclopedia
quantum mechanics -- a first quantised or semi-classical theory in which particle properties are quantised, but not particle numbers, fields and fundamental interactions.
quantum field theory or QFT -- a second or canonically quantised theory in which all aspects of particles, fields and interactions are quantised, with the exception of gravitation.
Quantum electrodynamics, quantum chromodynamics and electroweak theory are examples of relativistic fundamental QFTs which taken together form the Standard Model.
en.wikipedia.org /wiki/Quantum_physics   (229 words)

  
 Quantum Mechanics - Some Articles
The quantum mechanics explanations had strong scientific as well as spiritual or philosophic implications, since the influence of each electron from any atom could be found everywhere, leading to the notion that everything, everywhere is potentially in touch with everything else...
Quantum mechanics opened the discussion about reality really is (no pun intended), since the theory points presents a quite different aproach to order, solidity, determinism and mechanicism that shakes our classic view of "things".
Quantum mechanics has successfully challenged the belief that the observer is independent of the reality and has no influence on what is being observed.
www.thequantumsite.com   (796 words)

  
 Theory: Quantum Mechanics
Quantum mechanics is the description of physics at the scale of atoms, and the even smaller scales of fundamental particles.
Quantum theory is the language of all particle theories.
The rule for probability in quantum mechanics is that probability is the square of the absolute value of the relevant probability amplitude.
www2.slac.stanford.edu /vvc/theory/quantum.html   (1038 words)

  
 Quantum Mechanics
Quantum mechanics, the branch of mathematical physics that deals with atomic and subatomic systems and their interaction with radiation in terms of observable quantities.
True quantum mechanics appeared in 1926, reaching fruition nearly simultaneously in a variety of forms--namely, the matrix theory of Max Born and Werner Heisenberg, the wave mechanics of Louis V. de Broglie and Erwin Schrdinger, and the transformation theory of P.A.M. Dirac and Pascual Jordan.
According to quantum theory, electromagnetic radiation does not always consist of continuous waves; instead it must be viewed under some circumstances as a collection of particle-like photons, the energy and momentum of each being directly proportional to its frequency (or inversely proportional to its wavelength, the photons still possessing some wavelike characteristics).
www.mtmi.vu.lt /pfk/funkc_dariniai/quant_mech   (1410 words)

  
 quantum theory. The Columbia Encyclopedia, Sixth Edition. 2001-05
Quantum mechanics, the final mathematical formulation of the quantum theory, was developed during the 1920s.
The wave mechanics of Erwin Schrödinger (1926) involves the use of a mathematical entity, the wave function, which is related to the probability of finding a particle at a given point in space.
Quantum mechanics was combined with the theory of relativity in the formulation of P. Dirac (1928), which, in addition, predicted the existence of antiparticles.
www.bartleby.com /65/qu/quantumt.html   (795 words)

  
 Does God play dice? (December 2005) - Physics World - PhysicsWeb
Einstein was one of the founders of quantum mechanics, yet he disliked the randomness that lies at the heart of the theory.
Quantum mechanics could well relate to micro-physics the same way that thermodynamics relates to molecular physics: it is formally correct, but it may well be possible to devise deterministic laws at the micro scale.
Essentially, this is due to the phenomenon we call quantum interference between histories, which is due, in turn, to the way we calculate the quantum measure of a bunch of histories as the square of the sum of the amplitudes of the histories in the bunch.
www.physicsweb.org /articles/world/18/12/2/1   (2861 words)

  
 Quantum Mechanics
Quantum mechanics is a mathematical theory that can describe the behavior of objects that are roughly 10,000,000,000 times smaller than a typical human being.
The approach adopted in all textbooks on quantum mechanics is that the mathematical solution of model problems brings insight in the physics of quantum phenomena.
Watching a quantum system evolve in time is a very effective method to get acquainted with the basic features and peculiarities of quantum mechanics.
rugth30.phys.rug.nl /quantummechanics   (472 words)

  
 Quantum Mechanics
According to the quantum theory, energy is emitted and absorbed in a small packet, called a quantum (pl. quanta), which in some situations behaves as particles of matter do; particles exhibit certain wavelike properties when in motion and are no longer viewed as localized in a given region but as spread out to some degree.
Quantum mechanics is needed to explain many properties of matter, such as the temperature dependence of the specific heat of solids, as well as when very small quantities of matter or energy are involved, as in the interaction of elementary particles and fields, but the theory of
Niels Bohr used the quantum theory in 1913 to explain both atomic structure and atomic spectra, showing the connection between the energy levels of an atom's electrons and the frequencies of light given off and absorbed by the atom.
www.neutron.anl.gov /hyper-physics/Quantum-mechanics.html   (611 words)

  
 Quantum Mechanics
Quantum mechanics is founded on the concept that quantum events occur according to finite probabilities within finite time intervals.
Quantum mechanics merely shows us that in the micro world of particle physics man is limited in his ability to measure quantum effects.
Since quantum entities at any moment have the potential to behave either as particles or as waves, it is impossible, for example, to accurately measure both the position and the momentum of such an entity (the Heisenberg uncertainty principle).
www.reasons.org /resources/apologetics/quantummech.shtml   (2715 words)

  
 Quantum Mechanics
In quantum mechanical contexts, the term ‘observable’ is used interchangeably with ‘physical quantity’, and should be treated as a technical term with the same meaning.
In standard texts on quantum mechanics, the vector is represented by a function known as the wave-function, or ψ-function.
From a mathematical point of view, what really distinguishes quantum mechanics from its classical predecessors is that states and quantities have a richer structure; they form families with a more interesting network of relations among their members.
plato.stanford.edu /entries/qm   (3810 words)

  
 Copenhagen Interpretation of Quantum Mechanics
Hence in the search for a theory of quantum mechanics it became a methodological requirement to Bohr that any further theory of the atom should predict values in domains of large quantum numbers that should be a close approximation to the values of classical physics.
The quantum mechanical description of the object differs from the classical description of the measuring apparatus, and this requires that the object and the measuring device should be separated in the description, but the line of separation is not the one between macroscopic instruments and microscopic objects.
In general, Bohr considered the demands of complementarity in quantum mechanics to be logically on a par with the requirements of relativity in the theory of relativity.
plato.stanford.edu /entries/qm-copenhagen   (4400 words)

  
 Quantum Mechanics Examples
Quantum descriptions must be quite different because quantum mechanics asserts that a particle does not have a position and a velocity.
The aim of quantum mechanics is to calculate this range of possible particle positions and the relative probability of those positions.
In quantum mechanics the topic is the motion of an electron under the influence of the electrostatic attractive force of the nucleus...atomic physics.
www.physics.csbsju.edu /QM   (2551 words)

  
 Quantum mechanics history
Einstein proposed a quantum theory of light to solve the difficulty and then he realised that Planck's theory made implicit use of the light quantum hypothesis.
Heisenberg wrote his first paper on quantum mechanics in 1925 and 2 years later stated his uncertainty principle.
Dirac, in 1928, gave the first solution of the problem of expressing quantum theory in a form which was invariant under the Lorentz group of transformations of special relativity.
www-groups.dcs.st-and.ac.uk /~history/HistTopics/The_Quantum_age_begins.html   (1625 words)

  
 Quantum Mechanics, 1925-1927: The Quantum Mechanic
The present paper seeks to establish a basis for theoretical quantum mechanics founded exclusively upon relationships between quantities which in principle are observable.
The wave mechanics appealed to many physicists because it seemed to do everything that matrix mechanics could do but much more easily and seemingly without giving up the visualization of orbits within the atom.
This unleashed an intense debate between the followers of the alternative versions of quantum mechanics that formed the background to the later uncertainty relations and the Copenhagen Interpretation.
www.aip.org /history/heisenberg/p07.htm   (527 words)

  
 Amazon.com: Quantum Mechanics (Physics): Books: Albert Messiah   (Site not responding. Last check: 2007-10-21)
Chapter 4 is an overview of the statistical interpretation of quantum mechanics.
Any textbook on quantum mechanics at this level in the 21st century should include a very detailed introduction to numerical methods so as to prepare the student early on to techniques that will be used more and more in the decades ahead.
Although the presentation of the material still assumes a knowledge of classical mechanics and magnetism (an approach that has since been abandoned in quantum mechanics texts), the book is remarkably self-contained (the exercises, however, are not).
www.amazon.com /Quantum-Mechanics-Physics-Albert-Messiah/dp/0486409244   (2282 words)

  
 Physics Encyclopedia: Quantum Mechanics
Quantum Mechanics I - a comprehensive undergrad lecture course by N. Walet - from fl body radiation up to 3D Scroedinger equation.
Quantum Mechanics I from MIT - an extensive collection of lectures notes on different aspects of QM.
Quantum states in the light field - quantum noise, sqeezed states etc.
members.tripod.com /~IgorIvanov/physics/qm.html   (214 words)

  
 Quantum Mechanics
These were the laws of quantum mechanics, and they got their name from the work of Max Planck.
Here's one of the quirky things about quantum mechanics: just because an electron or a photon can be thought of as a particle, doesn't mean they can't still be though of as a wave as well.
Scientists interpret quantum mechanics to mean that a tiny piece of material like a photon or electron is both a particle and a wave.
www.pbs.org /transistor/science/info/quantum.html   (984 words)

  
 Open Directory - Science: Physics: Quantum Mechanics
Intro to Quantum Mechanics - This page is intended to give an ordinary person a brief overview of the importance and wonder of quantum mechanics.
Student Understanding of Quantum Mechanics - A set of lectures and reports outlining methods of teaching introductory quantum mechanics to a wide range of students.
Topics in Modern Quantum Optics - This is the written version of lectures presented at the 17th Symposium on Theoretical Physics covering various topics in quantum optics.
www.dmoz.org /Science/Physics/Quantum_Mechanics   (718 words)

  
 Introduction
Newtonian mechanics (1687) explained the motion of mechanical objects on both celestial and terrestrial scales.
The old quantum theory, resulting in Bohr's orbital model of the atom could point to certain real successes: Derivation of the Balmer formula, quantum numbers and selection rules for energy states in an atom, explanation of the periodic table and the Pauli exclusion principle.
The theory of quantum mechanics asserts that with every possibility for an event in nature to take place, there is a quantity called amplitude associated with each alternative.
rugth30.phys.rug.nl /quantummechanics/intro.htm   (896 words)

  
 Kantian Quantum Mechanics, Metaphysic of Space
Classic quantum mechanics seems to exhibit some of the characteristics that Immanuel Kant described about the relation between phenomenal reality in space and time and things-in-themselves.
Although chance in quantum mechanics has often been argued as allowing for free will, a free cause is still a very different thing from a random cause, which doesn't need mind or self or intention.
As a good quantum theory, the "quantum potential" field theory also might be expected to postulate the existence of particles that mediate the field, but this does not seem to be part of it -- and it would be awkward, because even virtual particles, which mediate forces in quantum mechanics, observe the limitations of Relativity.
www.friesian.com /space-2.htm   (5616 words)

  
 Open Directory - Science: Physics: Quantum Mechanics: Interpretations
Indeterminism and the Bohm Interpretation of Quantum Mechanics - In this essay it is argued that it is possible to subscribe to the Bohm interpretation of quantum mechanics without giving up indeterminism in nature.
Measurement in Quantum Theory - Collapse of the wave function, role of the observer in QM; From the Stanford Encyclopedia, by Henry Krips.
Relational Quantum Mechanics - An interpretation of quantum theory which discards the notions of absolute state of a system, absolute value of its physical quantities, or absolute event; from the Stanford Encyclopedia of Philosophy by Federico Laudisa and Carlo Rovelli.
dmoz.org /Science/Physics/Quantum_Mechanics/Interpretations   (677 words)

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