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# Topic: Feynman diagram

 Feynman diagram - Wikipedia, the free encyclopedia A Feynman diagram is therefore a symbolic notation for the factors appearing in each term of the Dyson series. Feynman diagram and path integral methods are also used in statistical mechanics. John Ellis was the first to refer to a certain class of Feynman diagrams as penguin diagrams, due in part to their shape, and in part to a legendary bar-room bet with Melissa Franklin (the loser reportedly had to incorporate the term "penguin" into their next research paper). en.wikipedia.org /wiki/Feynman_diagram   (1193 words)

 One-loop Feynman diagram - Wikipedia, the free encyclopedia In physics, a one-loop Feynman diagram is a connected Feynman diagram with only one cycle (unicyclic). Such a diagram can be obtained from a tree diagram by adding an edge connecting two internal vertices (of course, this is only possible in general if we ignore the vertex matching rules). The evaluation of one-loop Feynman diagrams usually leads to divergent expressions, which are either due to zero-mass particles in the cycle of the diagram (infrared divergence) or due to insufficient falloff of the integrand for high momenta (ultraviolet divergence). en.wikipedia.org /wiki/One-loop_Feynman_diagram   (258 words)

 Atoms - the inside story. Feynman diagrams.   (Site not responding. Last check: 2007-11-06) Feynman diagrams are useful for showing interactions between two (or more) particles. Feynman suggested that a positron (or any other antiparticle) is like a particle travelling backwards in time. Feynman diagrams can also be used to describe the strong nuclear force. www.schoolscience.co.uk /content/5/physics/particles/partich6pg3.html   (484 words)

 Exchange Particles Gluon interactions are often represented by a Feynman diagram. Developed by Feynman to decribe the interactions in quantum electrodynamics (QED), the diagrams have found use in describing a variety of particle interactions. The weak interaction visualized in the Feynman diagram below is responsible for the decay of the neutron and for beta decay. hyperphysics.phy-astr.gsu.edu /hbase/particles/expar.html#c1   (1159 words)

 Science News Created by Feynman in the 1940s to solve one of the most vexing puzzles of theoretical physics at the time—a feat for which he would share the 1965 Nobel Prize in Physics—the drawings give physicists a quick, intuitive way to organize and understand difficult calculations. This example was one that Feynman presented at the diagrams' flop of a debut, and it was also one of the first Feynman diagrams to be published. On May 11, 1998, Feynman diagrams were briefly in the public eye when a post office in Lake Worth, Fla., used one of them as its stamp cancellation to honor Richard Feynman, who had died in February of that year, on what would have been his 80th birthday. www.phschool.com /science/science_news/articles/dr_feynman.html   (2486 words)

 Body Diagram -- Recommendations and Resources   (Site not responding. Last check: 2007-11-06) Drawing a free body diagram is a method often used by physicists working out kinetics or other mechanics problems to show all the mechanical vector forces acting on the given free body (or bodies) at any given time. A diagram is a simplified and structured visual representation of concepts, ideas, constructions, relations, statistical data, anatomy etc used in all aspects of human activities to visualize and clarify the topic. A Feynman diagram is a bookkeeping device for performing calculations in quantum field theory, invented by American physicist Richard Feynman. www.becomingapediatrician.com /health/19/body-diagram.html   (848 words)

 Examples of the use of Feynman vertices to describe processes The Feynman diagram for the d to u transition is a combination of quark-W vertex and same generation lepton W vertex. The Feynman diagram is a simple combination of a quark weak vertex and a lepton-weak vertex. The Feynman diagram illustrates that the reaction is a combination of a quark weak vertex and a weak-lepton vertex. teachers.web.cern.ch /teachers/archiv/HST2002/feynman/examples.htm   (1005 words)

 Theory: Feynman Diagrams Because Feynman diagrams represent terms in a quantum calculation, the intermediate stages in any diagram cannot be observed. The Feynman Rules for a theory are very simple, but lead to increasingly complicated mathematical expressions as increasingly complicated diagrams are constructed. Where each diagram has a closed loop, there is an arbitrary momentum and energy flow around the loop and we must integrate over all possible choices for these quantities. www2.slac.stanford.edu /vvc/theory/feynman.html   (811 words)

 Hey Feynman - Articles - Physics - Feynman Diagrams   (Site not responding. Last check: 2007-11-06) The diagram as shown, but with the (virtual) photon disintegrating into a positron-electron pair, annihilating into a new photon, and getting absorbed into the other electron. Again, none of the supposed activity in the middle of the diagram is observed, but by calculating these additional possibilities, the theoretical numbers match even MORE closely the probabilities observed in experiment. You could also have a diagram with two photons being emitted and absorbed, or a diagram in which one photon goes out and back into the electron on the left, and the other photon goes out from the left electron and across to the photon on the right. www.heyfeynman.com /article_info.php?articles_id=13   (1112 words)

 Like Chocolate for String Theory In general, the more complicated the diagram, the less likely the process depicted in that diagram is to happen, so you can cut off the calculation at any level of complexity and get a corresponding level of accuracy. This diagram represents a “vacuum” exchange of three gluons—in other words, a triple-gluon swap between two particles that aren’t there; in quantum mechanics, empty space is filled with “virtual” particles that pop into being from nothingness and promptly disappear again. Because the Feynman diagrams are so intractable, the other folks have resorted to something called lattice gauge theory, in which space-time is divided into a finite set of points, called a lattice. pr.caltech.edu /periodicals/EandS/articles/LXVI3/choco.html   (3132 words)

 Feynman on Gravity Feynman shows that the spin-zero theory predicts that the gravity attraction between hot regions of gas is smaller than for cool regions. Feynman analyzes the precession of the orbit of the planet Mercury in the classical limit of his linearized theory and finds that the prediction is too large by a factor of 4/3. This is Feynman's intuitive way of defining the formal forbidding mathematical idea of "diffeomorphism" invariance which is the new symmetry principle of the general relativity of curved spacetime that is different from, but in addition to, the locally flat Lorentz boost symmetry of special relativity. www.qedcorp.com /pcr/pcr/feynman/feyngrav.html   (12007 words)

 The Weirdo Pages: Richard Feynman Inventing the bit of scientific notation later known as the Feynman diagram. Feynman was a practical joker, a painter, a bongo player, and always a showman. While watching "Trinity," the first atomic bomb test, in 1945, Feynman decided no one really knew if the explosion would be bright enough to damage the eye, so he watched it directly through the windshield of his truck. www.crunchygods.com /weirdo/feynman   (455 words)

 Feynman Diagram Samples   (Site not responding. Last check: 2007-11-06) Over 165 Feynman diagrams can be downloaded here and used for your own projects. Multiple Feynman diagrams are packed onto a single diagram file. A wide selection of diagrams (over 70) based on "A Guide to Feynman Diagrams in the Many-Body Problem" by Richard D. Mattuck are provided. www.feyndraw.com /samples.html   (137 words)

 Dr. Feynman's Doodles: Science News Online, July 16, 2005   (Site not responding. Last check: 2007-11-06) Consider the Feynman diagram (above) that looks a bit like a person in a spread-eagle stance. A lot of people ask how someone like Richard Feynman, who played the bongo drums, loved practical jokes, and was an amateur safecracker and a bon vivant, could also win a Nobel Prize in Physics. In psychiatrist Carl Jung's terms, Feynman was an extraverted (Jung's spelling), intuitive type. www.sciencenews.org /articles/20050716/bob9.asp   (2631 words)

 Feynman Diagrams   (Site not responding. Last check: 2007-11-06) It began with the Feynman diagram which I introduced earlier in the context of relativistic kinematics. The simplest case is the ``first-order'' diagram in Fig. Each diagram, you see, is rigourously equivalent to a big messy integral which is definitely less appealing to the brain's right hemisphere; but the big integral can be evaluated to give the correct formula for the interaction of the two electrons to that order in musr.physics.ubc.ca /~jess/p200/hep/node2.html   (292 words)

 Feynman diagram - QuickSeek Encyclopedia   (Site not responding. Last check: 2007-11-06) In this Feynman diagram, electrons annihilate and become a quark-antiquark pair. The value of a given diagram can be derived from the graph; the value of the interaction as a whole is gotten by summing over all diagrams. Feynman Rules.it a kind and detailed introduction for italian studentsde:Feynman-Diagramm feynmandiagram.quickseek.com   (1157 words)

 Feynman Diagrams   (Site not responding. Last check: 2007-11-06) The little diagram inside the cargo bay tells us exactly what went on here, and since it does such a fine job of explaining the interaction between two humans, I am going to refer to it as the fine man diagram (pun definitely intended). From this point, it is easy to replace A and B in the fine man diagram with two particles of like charge, say two electrons, replace the wrench with a photon, and we have the Feynman diagram for a typical electromagnetic interaction (Figure 2). Of course this is only the beginning of the usefulness of Feynman diagrams; they permeate high energy physics today, and it is hard to imagine discussing particle interactions without them. home.fnal.gov /~bugel/fineman.html   (1166 words)

 Creating Feynman Diagrams with LaTex   (Site not responding. Last check: 2007-11-06) This document is a tutorial on creating Feynman diagrams in LaTex for the CU Supersymmetry analysis group. are predefined to the four corners of the diagram (``north-east'' etc.). The diagram is completed in lines 30--33 by placing dots at all internal vertices. hep-www.colorado.edu /~nlc/software/feyntex_ruddick.html   (466 words)

 Automation of Feynman diagram evaluation (ResearchIndex)   (Site not responding. Last check: 2007-11-06) Abstract: A C-program DIANA (DIagram ANAlyser) for the automation of Feynman diagram evaluations is presented. For specific processes thousands of multiloop Feynman diagrams do contribute, and it turns out to be impossible to perform these calculations by hand. 1 A Feynman Diagram Analyser DIANA (context) - Fleischer, Tentukov citeseer.ist.psu.edu /420279.html   (244 words)

 Feynman Diagrams and Forces Between Particles   (Site not responding. Last check: 2007-11-06) These events are represented by a single vertex in a Feynman diagram. The strength of the force is given by the intensity of the field which is proportional to the number of photons; hence the greater the force on a particle the more photons it will emit or absorb. The range of a force may be understood in terms of exchange of field quanta too.The electromagnetic force, which has infinite range is due to the exchange of photons which travel at light speed and thus have zero rest mass in accordance with Special Relativity. www.egglescliffe.org.uk /physics/particles/parts/parts1.html   (1055 words)

 Richard P. Feynman News Five CDs featuring Richard Feynman drumming and recounting some of his most well-liked stories are now available for download (for a fee) at the TuvaMuch section of lulu.com. Readings from Feynman’s best-selling books by film and television actor Norman Parker, and a drumming performance and reminiscences of what it was like to drum with Feynman by Ralph Leighton and Tom Rutishauser. With missives to and from scientific luminaries, as well as letters to and from fans, family, students, crackpots, as well as everyday people eager for Feynman’s wisdom and counsel, the result is a wonderful de facto guide to life, and eloquent testimony to the human quest for knowledge at all levels. www.fotuva.org /online/news.html   (3089 words)

 Feynman Diagram Drawing Program: FeynDraw   (Site not responding. Last check: 2007-11-06) FeynDraw was developed because of a lack of a sophisticated drawing product for the Windows environment which could be used to generate Feynman or topological diagrams and provide images for use on the internet and in publications. We also have available on our linked Feynman Diagram Samples page a large number of sample diagrams predrawn. These can be used directly or as a source of components for your own diagrams. www.feyndraw.com   (527 words)

 Diana homepage   (Site not responding. Last check: 2007-11-06) There are several FORM packages for evaluating multiloop diagrams, like MINCER, and a package by L.Avdeev for the calculation of 3-loop bubble integrals with one non-zero mass. To deal with thousands of diagrams, it is necessary to use special techniques like databases and special controlling programs. It appears absolutely necessary that various groups produce their own solutions of handling the problem of automation: various ways will be of different efficiency, have different domains of applicability, and last but not least, should eventually allow for completely independent checks of the final results. www.physik.uni-bielefeld.de /~tentukov/diana.html   (1025 words)

 Feynman Diagram Looking at this diagram http://www.mov.vic.gov.au/scidiscove...01708_w150.jpg which shows two electrons repelling, I don't understand why the vertex of the electron on the right is higher than that of the left. As far as the part of your question about one vertex being higher than the other, I believe it is conventional for particle physicists to let time be the vertical axis and a dimension of space be the horizontal axis when they draw Feynman diagrams. So you could interpret the diagram as meaning the particle on the left emits a virtual photon, and some time later the particle on the right absorbs it. www.physicsforums.com /showthread.php?p=224415   (437 words)

 A Spinor Technique in Symbolic Feynman Diagram Calculation -- from Mathematica Information Center We present a recursive diagrammatic method for evaluating tree-level Feynman diagrams involving multi-fermions which interact through gauge bosons (gluons or photons). Based on this method, a package called COMPUTE, which can generate and calculate all the possible Feynman diagrams for exclusive processes in perturbative QCD, has been developed (available in both Mathematica and Maple). As an example, a calculation of the nucleon Compton scattering amplitude is given. library.wolfram.com /infocenter/Articles/3280   (88 words)

 Citebase - A Feynman Diagram Analyser DIANA Authors: Tentyukov, M. Fleischer, J. A C-program DIANA (DIagram ANAlyser) for the automatic Feynman diagram evaluation is presented. It consists of two parts: the analyzer of diagrams and the interpreter of a special text manipulating language. A FORM based package (ON-SHELL2) for the calculation of two loop self-energy diagrams with one nonzero mass in internal lines and the external momentum on the same mass shell is elaborated. citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:hep-ph/9904258   (976 words)

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