Physics and Feynman's Diagrams
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External Fields and Measuring Radiative Corrections
Quantum Electrodynamics (QED), Winter 2015/16 Radiative corrections External fields and measuring radiative corrections We now briefly describe how the radiative corrections Πc(k), Σc(p) and Λc(p1; p2), the finite parts of the loop diagrams which enter in renormalization, lead to observable effects. We will consider the two classic cases: the correction to the electron magnetic moment and the Lamb shift. Both are measured using a background electric or magnetic field. Calculating amplitudes in this situation requires a modified perturbative expansion of QED from the one we have considered thus far. Feynman rules with external fields An important approximation in QED is where one has a large background electromagnetic field. This external field can effectively be treated as a classical background in which we quantise the fermions (in analogy to including an electromagnetic field in the Schrodinger¨ equation). More formally we can always expand the field operators around a non-zero value (e) Aµ = aµ + Aµ (e) where Aµ is a c-number giving the external field and aµ is the field operator describing the fluctua- tions. The S-matrix is then given by R 4 ¯ (e) S = T eie d x : (a=+A= ) : For a static external field (independent of time) we have the Fourier transform representation Z (e) 3 ik·x (e) Aµ (x) = d= k e Aµ (k) We can now consider scattering processes such as an electron interacting with the background field. We find a non-zero amplitude even at first order in the perturbation expansion. (Without a background field such terms are excluded by energy-momentum conservation.) We have Z (1) 0 0 4 (e) hfj S jii = ie p ; s d x : ¯A= : jp; si Z 4 (e) 0 0 ¯− µ + = ie d x Aµ (x) p ; s (x)γ (x) jp; si Z Z 4 3 (e) 0 µ ik·x+ip0·x−ip·x = ie d x d= k Aµ (k)u ¯s0 (p )γ us(p) e ≡ 2πδ(E0 − E)M where 0 (e) 0 M = ieu¯s0 (p )A= (p − p)us(p) We see that energy is conserved in the scattering (since the external field is static) but in general the initial and final 3-momenta of the electron can be different. -
Lecture Notes Particle Physics II Quantum Chromo Dynamics 6
Lecture notes Particle Physics II Quantum Chromo Dynamics 6. Feynman rules and colour factors Michiel Botje Nikhef, Science Park, Amsterdam December 7, 2012 Colour space We have seen that quarks come in three colours i = (r; g; b) so • that the wave function can be written as (s) µ ci uf (p ) incoming quark 8 (s) µ ciy u¯f (p ) outgoing quark i = > > (s) µ > cy v¯ (p ) incoming antiquark <> i f c v(s)(pµ) outgoing antiquark > i f > Expressions for the> 4-component spinors u and v can be found in :> Griffiths p.233{4. We have here explicitly indicated the Lorentz index µ = (0; 1; 2; 3), the spin index s = (1; 2) = (up; down) and the flavour index f = (d; u; s; c; b; t). To not overburden the notation we will suppress these indices in the following. The colour index i is taken care of by defining the following basis • vectors in colour space 1 0 0 c r = 0 ; c g = 1 ; c b = 0 ; 0 1 0 1 0 1 0 0 1 @ A @ A @ A for red, green and blue, respectively. The Hermitian conjugates ciy are just the corresponding row vectors. A colour transition like r g can now be described as an • ! SU(3) matrix operation in colour space. Recalling the SU(3) step operators (page 1{25 and Exercise 1.8d) we may write 0 0 0 0 1 cg = (λ1 iλ2) cr or, in full, 1 = 1 0 0 0 − 0 1 0 1 0 1 0 0 0 0 0 @ A @ A @ A 6{3 From the Lagrangian to Feynman graphs Here is QCD Lagrangian with all colour indices shown.29 • µ 1 µν a a µ a QCD = (iγ @µ m) i F F gs λ j γ A L i − − 4 a µν − i ij µ µν µ ν ν µ µ ν F = @ A @ A 2gs fabcA A a a − a − b c We have introduced here a second colour index a = (1;:::; 8) to label the gluon fields and the corresponding SU(3) generators. -
Wolfgang Pauli Niels Bohr Paul Dirac Max Planck Richard Feynman
Wolfgang Pauli Niels Bohr Paul Dirac Max Planck Richard Feynman Louis de Broglie Norman Ramsey Willis Lamb Otto Stern Werner Heisenberg Walther Gerlach Ernest Rutherford Satyendranath Bose Max Born Erwin Schrödinger Eugene Wigner Arnold Sommerfeld Julian Schwinger David Bohm Enrico Fermi Albert Einstein Where discovery meets practice Center for Integrated Quantum Science and Technology IQ ST in Baden-Württemberg . Introduction “But I do not wish to be forced into abandoning strict These two quotes by Albert Einstein not only express his well more securely, develop new types of computer or construct highly causality without having defended it quite differently known aversion to quantum theory, they also come from two quite accurate measuring equipment. than I have so far. The idea that an electron exposed to a different periods of his life. The first is from a letter dated 19 April Thus quantum theory extends beyond the field of physics into other 1924 to Max Born regarding the latter’s statistical interpretation of areas, e.g. mathematics, engineering, chemistry, and even biology. beam freely chooses the moment and direction in which quantum mechanics. The second is from Einstein’s last lecture as Let us look at a few examples which illustrate this. The field of crypt it wants to move is unbearable to me. If that is the case, part of a series of classes by the American physicist John Archibald ography uses number theory, which constitutes a subdiscipline of then I would rather be a cobbler or a casino employee Wheeler in 1954 at Princeton. pure mathematics. Producing a quantum computer with new types than a physicist.” The realization that, in the quantum world, objects only exist when of gates on the basis of the superposition principle from quantum they are measured – and this is what is behind the moon/mouse mechanics requires the involvement of engineering. -
Biographical References for Nobel Laureates
Dr. John Andraos, http://www.careerchem.com/NAMED/Nobel-Biographies.pdf 1 BIOGRAPHICAL AND OBITUARY REFERENCES FOR NOBEL LAUREATES IN SCIENCE © Dr. John Andraos, 2004 - 2021 Department of Chemistry, York University 4700 Keele Street, Toronto, ONTARIO M3J 1P3, CANADA For suggestions, corrections, additional information, and comments please send e-mails to [email protected] http://www.chem.yorku.ca/NAMED/ CHEMISTRY NOBEL CHEMISTS Agre, Peter C. Alder, Kurt Günzl, M.; Günzl, W. Angew. Chem. 1960, 72, 219 Ihde, A.J. in Gillispie, Charles Coulston (ed.) Dictionary of Scientific Biography, Charles Scribner & Sons: New York 1981, Vol. 1, p. 105 Walters, L.R. in James, Laylin K. (ed.), Nobel Laureates in Chemistry 1901 - 1992, American Chemical Society: Washington, DC, 1993, p. 328 Sauer, J. Chem. Ber. 1970, 103, XI Altman, Sidney Lerman, L.S. in James, Laylin K. (ed.), Nobel Laureates in Chemistry 1901 - 1992, American Chemical Society: Washington, DC, 1993, p. 737 Anfinsen, Christian B. Husic, H.D. in James, Laylin K. (ed.), Nobel Laureates in Chemistry 1901 - 1992, American Chemical Society: Washington, DC, 1993, p. 532 Anfinsen, C.B. The Molecular Basis of Evolution, Wiley: New York, 1959 Arrhenius, Svante J.W. Proc. Roy. Soc. London 1928, 119A, ix-xix Farber, Eduard (ed.), Great Chemists, Interscience Publishers: New York, 1961 Riesenfeld, E.H., Chem. Ber. 1930, 63A, 1 Daintith, J.; Mitchell, S.; Tootill, E.; Gjersten, D., Biographical Encyclopedia of Scientists, Institute of Physics Publishing: Bristol, UK, 1994 Fleck, G. in James, Laylin K. (ed.), Nobel Laureates in Chemistry 1901 - 1992, American Chemical Society: Washington, DC, 1993, p. 15 Lorenz, R., Angew. -
Path Integral and Asset Pricing
Path Integral and Asset Pricing Zura Kakushadze§†1 § Quantigicr Solutions LLC 1127 High Ridge Road #135, Stamford, CT 06905 2 † Free University of Tbilisi, Business School & School of Physics 240, David Agmashenebeli Alley, Tbilisi, 0159, Georgia (October 6, 2014; revised: February 20, 2015) Abstract We give a pragmatic/pedagogical discussion of using Euclidean path in- tegral in asset pricing. We then illustrate the path integral approach on short-rate models. By understanding the change of path integral measure in the Vasicek/Hull-White model, we can apply the same techniques to “less- tractable” models such as the Black-Karasinski model. We give explicit for- mulas for computing the bond pricing function in such models in the analog of quantum mechanical “semiclassical” approximation. We also outline how to apply perturbative quantum mechanical techniques beyond the “semiclas- sical” approximation, which are facilitated by Feynman diagrams. arXiv:1410.1611v4 [q-fin.MF] 10 Aug 2016 1 Zura Kakushadze, Ph.D., is the President of Quantigicr Solutions LLC, and a Full Professor at Free University of Tbilisi. Email: [email protected] 2 DISCLAIMER: This address is used by the corresponding author for no purpose other than to indicate his professional affiliation as is customary in publications. In particular, the contents of this paper are not intended as an investment, legal, tax or any other such advice, and in no way represent views of Quantigic Solutions LLC, the website www.quantigic.com or any of their other affiliates. 1 Introduction In his seminal paper on path integral formulation of quantum mechanics, Feynman (1948) humbly states: “The formulation is mathematically equivalent to the more usual formulations. -
Richard P. Feynman Author
Title: The Making of a Genius: Richard P. Feynman Author: Christian Forstner Ernst-Haeckel-Haus Friedrich-Schiller-Universität Jena Berggasse 7 D-07743 Jena Germany Fax: +49 3641 949 502 Email: [email protected] Abstract: In 1965 the Nobel Foundation honored Sin-Itiro Tomonaga, Julian Schwinger, and Richard Feynman for their fundamental work in quantum electrodynamics and the consequences for the physics of elementary particles. In contrast to both of his colleagues only Richard Feynman appeared as a genius before the public. In his autobiographies he managed to connect his behavior, which contradicted several social and scientific norms, with the American myth of the “practical man”. This connection led to the image of a common American with extraordinary scientific abilities and contributed extensively to enhance the image of Feynman as genius in the public opinion. Is this image resulting from Feynman’s autobiographies in accordance with historical facts? This question is the starting point for a deeper historical analysis that tries to put Feynman and his actions back into historical context. The image of a “genius” appears then as a construct resulting from the public reception of brilliant scientific research. Introduction Richard Feynman is “half genius and half buffoon”, his colleague Freeman Dyson wrote in a letter to his parents in 1947 shortly after having met Feynman for the first time.1 It was precisely this combination of outstanding scientist of great talent and seeming clown that was conducive to allowing Feynman to appear as a genius amongst the American public. Between Feynman’s image as a genius, which was created significantly through the representation of Feynman in his autobiographical writings, and the historical perspective on his earlier career as a young aspiring physicist, a discrepancy exists that has not been observed in prior biographical literature. -
More Eugene Wigner Stories; Response to a Feynman Claim (As Published in the Oak Ridger’S Historically Speaking Column on August 29, 2016)
More Eugene Wigner stories; Response to a Feynman claim (As published in The Oak Ridger’s Historically Speaking column on August 29, 2016) Carolyn Krause has collected a couple more stories about Eugene Wigner, plus a response by Y- 12 to allegations by Richard Feynman in a book that included a story on his experience at Y-12 during World War II. … Mary Ann Davidson, widow of Jack Davidson, a longtime member of the Oak Ridge National Laboratory’s Instrumentation and Controls Division, told me about Jack’s encounter with Wigner one day. Once Eugene Wigner had trouble opening his briefcase while visiting ORNL. He was referred to Jack Davidson in the old Instrumentation and Controls Division. Jack managed to open it for him. As was his custom, Wigner asked Jack about his research. Jack, who later won an R&D-100 award, said he was building a camera that will imitate a fly’s eye; in other words, it will capture light coming from a variety of directions. The topic of television and TV cameras came up. Wigner said he wondered how TV works. So Davidson explained the concept to him. Charles Jones told me this story about Eugene Wigner when he visited ORNL in the 1980s. Jones, who was technical director of the Holifield Heavy Ion Research Facility, said he invited Wigner to accompany him to the top of the HHIRF tower, and Wigner happily accepted the offer. At the top Wigner looked down at all the ORNL buildings, most of which had been constructed after he was the lab’s research director in 1946-47. -
1 Drawing Feynman Diagrams
1 Drawing Feynman Diagrams 1. A fermion (quark, lepton, neutrino) is drawn by a straight line with an arrow pointing to the left: f f 2. An antifermion is drawn by a straight line with an arrow pointing to the right: f f 3. A photon or W ±, Z0 boson is drawn by a wavy line: γ W ±;Z0 4. A gluon is drawn by a curled line: g 5. The emission of a photon from a lepton or a quark doesn’t change the fermion: γ l; q l; q But a photon cannot be emitted from a neutrino: γ ν ν 6. The emission of a W ± from a fermion changes the flavour of the fermion in the following way: − − − 2 Q = −1 e µ τ u c t Q = + 3 1 Q = 0 νe νµ ντ d s b Q = − 3 But for quarks, we have an additional mixing between families: u c t d s b This means that when emitting a W ±, an u quark for example will mostly change into a d quark, but it has a small chance to change into a s quark instead, and an even smaller chance to change into a b quark. Similarly, a c will mostly change into a s quark, but has small chances of changing into an u or b. Note that there is no horizontal mixing, i.e. an u never changes into a c quark! In practice, we will limit ourselves to the light quarks (u; d; s): 1 DRAWING FEYNMAN DIAGRAMS 2 u d s Some examples for diagrams emitting a W ±: W − W + e− νe u d And using quark mixing: W + u s To know the sign of the W -boson, we use charge conservation: the sum of the charges at the left hand side must equal the sum of the charges at the right hand side. -
Scientific and Related Works of Chen Ning Yang
Scientific and Related Works of Chen Ning Yang [42a] C. N. Yang. Group Theory and the Vibration of Polyatomic Molecules. B.Sc. thesis, National Southwest Associated University (1942). [44a] C. N. Yang. On the Uniqueness of Young's Differentials. Bull. Amer. Math. Soc. 50, 373 (1944). [44b] C. N. Yang. Variation of Interaction Energy with Change of Lattice Constants and Change of Degree of Order. Chinese J. of Phys. 5, 138 (1944). [44c] C. N. Yang. Investigations in the Statistical Theory of Superlattices. M.Sc. thesis, National Tsing Hua University (1944). [45a] C. N. Yang. A Generalization of the Quasi-Chemical Method in the Statistical Theory of Superlattices. J. Chem. Phys. 13, 66 (1945). [45b] C. N. Yang. The Critical Temperature and Discontinuity of Specific Heat of a Superlattice. Chinese J. Phys. 6, 59 (1945). [46a] James Alexander, Geoffrey Chew, Walter Salove, Chen Yang. Translation of the 1933 Pauli article in Handbuch der Physik, volume 14, Part II; Chapter 2, Section B. [47a] C. N. Yang. On Quantized Space-Time. Phys. Rev. 72, 874 (1947). [47b] C. N. Yang and Y. Y. Li. General Theory of the Quasi-Chemical Method in the Statistical Theory of Superlattices. Chinese J. Phys. 7, 59 (1947). [48a] C. N. Yang. On the Angular Distribution in Nuclear Reactions and Coincidence Measurements. Phys. Rev. 74, 764 (1948). 2 [48b] S. K. Allison, H. V. Argo, W. R. Arnold, L. del Rosario, H. A. Wilcox and C. N. Yang. Measurement of Short Range Nuclear Recoils from Disintegrations of the Light Elements. Phys. Rev. 74, 1233 (1948). [48c] C. -
Old-Fashioned Perturbation Theory
2012 Matthew Schwartz I-4: Old-fashioned perturbation theory 1 Perturbative quantum field theory The slickest way to perform a perturbation expansion in quantum field theory is with Feynman diagrams. These diagrams will be the main tool we’ll use in this course, and we’ll derive the dia- grammatic expansion very soon. Feynman diagrams, while having advantages like producing manifestly Lorentz invariant results, give a very unintuitive picture of what is going on, with particles that can’t exist appearing from nowhere. Technically, Feynman diagrams introduce the idea that a particle can be off-shell, meaning not satisfying its classical equations of motion, for 2 2 example, with p m . They trade on-shellness for exact 4-momentum conservation. This con- ceptual shift was critical in allowing the efficient calculation of amplitudes in quantum field theory. In this lecture, we explain where off-shellness comes from, why you don’t need it, but why you want it anyway. To motivate the introduction of the concept of off-shellness, we begin by using our second quantized formalism to compute amplitudes in perturbation theory, just like in quantum mechanics. Since we have seen that quantum field theory is just quantum mechanics with an infinite number of harmonic oscillators, the tools of quantum mechanics such as perturbation theory (time-dependent or time-independent) should not have changed. We’ll just have to be careful about using integrals instead of sums and the Dirac δ-function instead of the Kronecker δ. So, we will begin by reviewing these tools and applying them to our second quantized photon. -
'Diagramology' Types of Feynman Diagram
`Diagramology' Types of Feynman Diagram Tim Evans (2nd January 2018) 1. Pieces of Diagrams Feynman diagrams1 have four types of element:- • Internal Vertices represented by a dot with some legs coming out. Each type of vertex represents one term in Hint. • Internal Edges (or legs) represented by lines between two internal vertices. Each line represents a non-zero contraction of two fields, a Feynman propagator. • External Vertices. An external vertex represents a coordinate/momentum variable which is not integrated out. Whatever the diagram represents (matrix element M, Green function G or sometimes some other mathematical object) the diagram is a function of the values linked to external vertices. Sometimes external vertices are represented by a dot or a cross. However often no explicit notation is used for an external vertex so an edge ending in space and not at a vertex with one or more other legs will normally represent an external vertex. • External Legs are ones which have at least one end at an external vertex. Note that external vertices may not have an explicit symbol so these are then legs which just end in the middle of no where. Still represents a Feynman propagator. 2. Subdiagrams A subdiagram is a subset of vertices V and all the edges between them. You may also want to include the edges connected at one end to a vertex in our chosen subset, V, but at the other end connected to another vertex or an external leg. Sometimes these edges connecting the subdiagram to the rest of the diagram are not included, in which case we have \amputated the legs" and we are working with a \truncated diagram". -
Works of Love
reader.ad section 9/21/05 12:38 PM Page 2 AMAZING LIGHT: Visions for Discovery AN INTERNATIONAL SYMPOSIUM IN HONOR OF THE 90TH BIRTHDAY YEAR OF CHARLES TOWNES October 6-8, 2005 — University of California, Berkeley Amazing Light Symposium and Gala Celebration c/o Metanexus Institute 3624 Market Street, Suite 301, Philadelphia, PA 19104 215.789.2200, [email protected] www.foundationalquestions.net/townes Saturday, October 8, 2005 We explore. What path to explore is important, as well as what we notice along the path. And there are always unturned stones along even well-trod paths. Discovery awaits those who spot and take the trouble to turn the stones. -- Charles H. Townes Table of Contents Table of Contents.............................................................................................................. 3 Welcome Letter................................................................................................................. 5 Conference Supporters and Organizers ............................................................................ 7 Sponsors.......................................................................................................................... 13 Program Agenda ............................................................................................................. 29 Amazing Light Young Scholars Competition................................................................. 37 Amazing Light Laser Challenge Website Competition.................................................. 41 Foundational