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Topic: Quantum field theory


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  Quantum field theory - Wikipedia, the free encyclopedia
Quantum field theory originated in the problem of computing the power radiated by an atom when it dropped from one quantum state to another of lower energy.
QFT, on the other hand, deals with fields on a fundamental level and particles only emerge as localized excitations (aka quanta aka quasiparticles) of the ground state (aka the vacuum) and it's precisely these quantum fields which correspond to the operator valued functions.
QFT most definitely isn't the same thing as classical field theory or classical field theory with some "minor" quantum corrections, which is a mistake many high energy physicists are prone to making at times, especially when working in the semiclassical approximation.
en.wikipedia.org /wiki/Quantum_field_theory   (3793 words)

  
 Kids.net.au - Encyclopedia Quantum field theory -   (Site not responding. Last check: 2007-10-22)
In particular, the quantum theory of the electromagnetic field, known as quantum electrodynamics, is one of the most well-tested and successful theories in physics.
It was discovered that quantum mechanical particles of the same species are indistinguishable, in the sense that the wavefunction of the entire system must be symmetric (bosons) or antisymmetric (fermions) when the coordinates of its consituent particles are exchanged.
The procedure by which quantum fields are constructed from individual particles was introduced by Dirac, and is (for historical reasons) known as second quantization[?].
www.kidsseek.com /encyclopedia-wiki/qu/Quantum_field_theory   (1627 words)

  
 The uncertain Universe - Quantum fields and unification - part 1 of 3
In 1900 Planck discovered the quantum in the transfer of energy from matter to radiation, and in 1905, Einstein's explanation of the photoelectric effect assumed that the transfer of energy from radiation to matter occurred in a similarly quantized fashion.
It is therefore hardly surprising that the development of quantum mechanics was soon followed by an attempt to formulate a quantum theory of electromagnetic radiation.
In quantum field theory all such particles are associated with quantum fields in much the same way that photons are associated with the electromagnetic field.
physicalworld.org /restless_universe/html/ru_5_21.html   (704 words)

  
 The search for a Quantum Field Theory
Quantum Field Theory purports to be the most fundamental of sciences in that it concerns the ultimate constituents of matter.
The term "quantum field theory" is used interchangeably with "particle physics" and "high energy physics" on the grounds that the experimental support for this theory comes from expensive experiments involving high-energy beams of particles.
Quantum chromodynamics, the gauge theory of quark colour is the candidate theory of the binding force, but we are limited by the fact that bound states cannot be done satisfactorily with quantum field theory.
www.cgoakley.demon.co.uk /qft   (5436 words)

  
 Quantum field theory
Quantum field theory (QFT) is the application of quantum mechanics to fieldss.
The fundamentals of quantum field theory were developed between the late 1920s and the 1950s, notably by Dirac, Fock, Pauli, Tomonaga, Schwinger, Feynman, and Dyson.
It was discovered that quantum mechanical particles of the same species are indistinguishable, in the sense that the wavefunction of the entire system must be symmetric (bosons) or antisymmetric (fermions) when the coordinates of its constituent particles are exchanged.
www.knowledgefun.com /book/q/qu/quantum_field_theory.html   (1066 words)

  
 A timeline of mathematics and theoretical physics
Gerard 't Hooft publishes his proof that the electroweak gauge theory of Weinberg is renormalizable and a new chapter in theoretical physics begins -- the age of quantum gauge field theory.
Quantum field theories with spacetime supersymmetry in four spacetime dimensions are discovered by Julius Wess and Bruno Zumino.
Stephen Hawking combines quantum field theory with classical general relativity and predicts that fl holes radiate through particle emission, behave as thermodynamic objects, and decay with a finite lifetime into objects that we don't yet understand.
superstringtheory.com /history/history3.html   (2102 words)

  
 Annotated Physics Encyclopædia: Quantum Field Theory
A Course of Field Theory from Univ of Leiden, 140 pp, with problems, 1.5Mb ps file (lectures), 0.5 Mb ps file (problems).
Quantum Field Theory program at IAS - a large number of lectures covering advanced and subtle issues of QFT; mainly in ps files.
Conformal field theory: a case study - (hep-th/9904145), introduction to Wess-Zumino-Witten model of 2D conformal field theory.
web.mit.edu /afs/athena.mit.edu/user/r/e/redingtn/www/netadv/qft.html   (217 words)

  
 Relativity and Quantum Theory   (Site not responding. Last check: 2007-10-22)
However, this theory is inherently a many-body theory with the quanta of the normal modes of the classical field having all the properties of physical particles.
Likewise, a continuous "chiral symmetry", normally exhibited by a theory of light quarks, is broken by the condensation of chirally oriented quark/anti-quark pairs in the vacuum.
The most successful numerical approach to quantum field theory begins with a formulation of quantum mechanics developed by Feynman in which a quantum amplitude is described as a weighted integral over all possible paths (not necessarily obeying the classical equations) which start at the system's initial state and end at the final state.
phys.columbia.edu /~cqft/physics.htm   (1637 words)

  
 Quantum Field Theory
Quantum field theory can be developed by adopting the path integral formulism as mentioned earlier, or by combining the field equation with canonical quantization as shown in the next sub-topic.
A renormalizable theory is one in which the details of a deeper scale are not needed to describe the physics at the present scale, save for a few experimentally measurable parameters (see more in the section about "Renormalizable Theories").
In quantum theory, the interaction between an electron and a magnetic field can be portrayed by the Feynman diagram in Figure 08a, which shows a photon from the magnetic field is absorbed by the electron and thus altered its trajectory.
universe-review.ca /R15-12-QFT.htm   (12130 words)

  
 Amazon.com: Quantum Field Theory in Condensed Matter Physics: Books: Alexei M. Tsvelik   (Site not responding. Last check: 2007-10-22)
Quantum field theory has been applied to many different areas of physics, and has done a fairly good job of explaining the phenomena in these areas.
Quantum field theory has yet to be put on a rigorous mathematical foundation, but this has not deterred its use in a myriad of applications, with condensed matter physics, the subject of this book, being one of them.
Explicit calculations are done for a bosonic field in an external field using the now ubiquitous mathematical identity that "the determinant of an operator is the exponential of the trace of the logarithm of the operator.
www.amazon.com /exec/obidos/tg/detail/-/0521589894?v=glance   (1896 words)

  
 quantum field theory. The Columbia Encyclopedia, Sixth Edition. 2001-05
study of the quantum mechanical interaction of elementary particles and fields.
Quantum field theory applied to the understanding of electromagnetism is called quantum electrodynamics (QED), and it has proved spectacularly successful in describing the interaction of light with matter.
Quantum field theory applied to the understanding of the strong interactions between quarks and between protons, neutrons, and other baryons and mesons is called quantum chromodynamics (QCD); QCD has a mathematical structure similar to that of QED.
www.bartleby.com /65/qu/quantumf.html   (180 words)

  
 Generalized Electroform Field Equations of Vector-Boson Field Theory : The Mirror-Image Maxwell's Equations for Long- ...
Instead, the GR grav-magnetic field is derived from artifactual off-diagonal components of the metric tensor in a way that injects the troublesome factor of 4 and spoils the Principle of Relativity from a forces point of view.
This book replaces classical General Relativity with a unified quantum field theory of forces in flat space with gravitational time-dilation only that still yields the 2nd-order classical GR effects, such as the perihelion precession of Mercury, the curvature of light around the Sun, and the gravitational red-shift.
On the fermion side of the unified field theory problem, the book introduces the Rishon sub-quarks proposed by Haim Harari and Micheal Shupe, treating the problem of the decay of the proton and deriving neutrino decay events that may be used to prove the Rishon sub-quark theory valid.
greenwdks.tripod.com /unifiedsummary.html   (3171 words)

  
 Logic as Boolean quantum field theory
Thus it seems that Boolean QFT is completely classical and the transition from classical mechanics to quantum theory could be regarded as a transition from binary QFT to complex QFT or from a binary logic to complex logic.
Amusingly, in the ordinary fermionic field theory the states created by a finite number of oscillator operators are the counterparts of the mutually consistent statements, their negations would correspond to a vacuum state obtained as an infinite product of all creation operators annihilated by creation operators.
This hierarchy corresponds to a hierarchy of quantizations in Boolean QFT.
www.physics.helsinki.fi /~matpitka/qlogic.html   (2449 words)

  
 Historical Notes: Quantum field theory
In standard approaches to quantum field theory one tends to think of particles as some kind of small perturbations in a field.
But it turns out that these field configurations are exactly the ones that satisfy the partial differential equations for the classical version of the field theory.
In the quantum case, a sign of confinement would be exponential decrease with spacetime area of the average phase of color flux through so-called Wilson loops - and this is achieved if there is in a sense maximal randomness in field configurations.
www.wolframscience.com /reference/notes/1061a   (912 words)

  
 Amazon.com: An Introduction to Quantum Field Theory: Books: Michael E. Peskin   (Site not responding. Last check: 2007-10-22)
When reading this book, and others on quantum field theory, I am always amazed at the degree to which it works, and its elegance, despite the fact that it really is a collection of ad hoc strategies and sophisticated guesswork.
Quantum Field Theory is a theory of modern physics which combines together quantum mechanics and special relativity and thus can be thought of as quantum mechanics in four space-time dimensions.
While the standard year-long field theory classes at our school's physics program are taught based on a set of recent lecture notes by a campus author (Srednicki), Peskin and Schroeder has always been cited as a recommended accompanying source for the courses.
www.amazon.com /exec/obidos/tg/detail/-/0201503972?v=glance   (2536 words)

  
 Non-equilibrium Quantum Field Theory
Specific problems that require non-equilibrium quantum field theoretic techniques for their solution include such diverse examples as topological transitions and electroweak baryogenesis, dynamics of the quark-gluon plasma and disoriented chiral condensates, effective field theories and the real-time renormalization group, and thermalization and reheating in the early universe.
The main focus of our research group has been on the development of field theory and numerical methods for attacking time evolution problems in quantum field theory such as the back-reaction of quantum fields on classical fields as well as the dynamics of non-equilibrium phase transitions.
A second set of problems is related to fundamental issues in field theoretic dynamical systems such as the quantum-to-classical transition, the dynamics of second order phase transitions and of nonlinear coherent structures, and the thermalization of quantum fields in initial value problems.
www.nersc.gov /news/greenbook/nersc3/node16.html   (391 words)

  
 Wiley::Quantum Field Theory, Revised Edition
The three main objectives are to explain the basic physics and formalism of quantum field theory, to make the reader fully proficient in theory calculations using Feynman diagrams, and to introduce the reader to gauge theories, which play such a central role in elementary particle physics.
The theory is applied to quantum electrodynamics (QED), where quantum field theory had its early triumphs, and to weak interactions where the standard electro-weak theory has had many impressive successes.
In order to help inexperienced research students grasp the meaning of the theory and learn to handle it confidently, the mathematical formalism is developed from first principles, its physical interpretation is stressed at every point and its use is illustrated in detailed applications.
eu.wiley.com /WileyCDA/WileyTitle/productCd-0471941867.html   (441 words)

  
 Quantum Field Theory   (Site not responding. Last check: 2007-10-22)
The new feature that is required in a successful union of quantum mechanics and special relativity is the possibility of the creation and annihilation of quanta (or `particles').
The framework in which quantum mechanics and special relativity are successfully reconciled is called quantum field theory.
Now the general principles on which quantum field theory are based actually allow for many different consistent theories to be constructed.
www.theory.caltech.edu /people/jhs/strings/str114.html   (465 words)

  
 Topological Quantum Field Theory
Besides general relativity and quantum field theory as usually practiced, a third sort of idealization of the physical world has attracted a great deal of attention in the last decade.
At first glance, general relativity and quantum theory look very different mathematically: one deals with space and spacetime, the other with Hilbert spaces and operators.
Quantum topology is very technical, as anything involving mathematical physicists inevitably becomes.
math.ucr.edu /home/baez/planck/node3.html   (1399 words)

  
 Quantum Field Theory
Quantum Field Theory (QFT) is perhaps the single most important concept in physics to be discovered in the twentieth century.
This volume projects the central theme through a selection of invited articles in the areas where the impact of QFT has been especially pronounced, from particle physics to string theory (with several interpolating stages of development), and extending to some facets of astrophysics and the physics of condensed matter.
In the area of particle physics the emphasis is mainly on symmetries, topologies, gauge theories and renormalization groups.
www.hindbook.com /Home.asp?P=76   (596 words)

  
 Algebraic Quantum Field Theory   (Site not responding. Last check: 2007-10-22)
Quantum Field Theory (QFT) is the general framework for the description of the physics of relativistic quantum systems, notably of elementary particles.
It is the synthesis of Quantum Theory and Special Relativity, supplemented by the principle of Locality in space and time, and by the Spectral Condition in energy and momentum.
Algebraic QFT (AQFT) emphasizes the role of algebraic relations among observables which determine, rather than quantum fields proper, a physical system.
unith.desy.de /research/aqft   (98 words)

  
 Introduction to Quantum Field Theory - Synopsis   (Site not responding. Last check: 2007-10-22)
Quantum field theory forms the backbone of many areas of theoretical physics, from gauge theories of particle physics to advanced condensed matter problems.
This 16-hour lecture course is intended as an introduction to the subject, taking the student from quantum mechanics to the formulation and solution of relativistic field theories in terms of path integrals.
A basic knowledge of classical, statistical and quantum mechanics will be assumed, together with complex variable calculus.
www-thphys.physics.ox.ac.uk /users/JohnCardy/coursedescription.html   (139 words)

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