Editing Feynman diagram (section)

== Representation of physical reality ==
In their presentations of [[fundamental interactions]],<ref>Gerardus 't Hooft, Martinus Veltman, ''Diagrammar'', CERN Yellow Report 1973, reprinted in G. 't Hooft, ''Under the Spell of Gauge Principle'' (World Scientific, Singapore, 1994), Introduction [http://preprints.cern.ch/cgi-bin/setlink?base=cernrep&categ=Yellow_Report&id=1973-009 online] {{Webarchive|url=https://web.archive.org/web/20050319203006/http://preprints.cern.ch/cgi-bin/setlink?base=cernrep&categ=Yellow_Report&id=1973-009 |date=2005-03-19 }}</ref><ref>Martinus Veltman, ''Diagrammatica: The Path to Feynman Diagrams'', Cambridge Lecture Notes in Physics, {{ISBN|0-521-45692-4}}</ref> written from the particle physics perspective, [[Gerard 't Hooft]] and [[Martinus Veltman]] gave good arguments for taking the original, non-regularized Feynman diagrams as the most succinct representation of the physics of quantum scattering of [[fundamental particles]]. Their motivations are consistent with the convictions of [[James Daniel Bjorken]] and [[Sidney Drell]]:<ref>{{cite book |first1=J. D. |last1=Bjorken |first2=S. D. |last2=Drell |title=Relativistic Quantum Fields |publisher=McGraw-Hill |location=New York |year=1965 |page=viii |isbn=978-0-07-005494-3}}</ref>

<blockquote>The Feynman graphs and rules of calculation summarize [[quantum field theory]] in a form in close contact with the experimental numbers one wants to understand. Although the statement of the theory in terms of graphs may imply [[perturbation theory (quantum mechanics)|perturbation theory]], use of graphical methods in the [[many-body problem]] shows that this formalism is flexible enough to deal with phenomena of nonperturbative characters ... Some modification of the [[Feynman rules]] of calculation may well outlive the elaborate mathematical structure of local canonical quantum field theory ...</blockquote>

In [[quantum field theories]], Feynman diagrams are obtained from a [[Lagrangian (field theory)|Lagrangian]] by Feynman rules.

[[Dimensional regularization]] is a method for [[regularization (physics)|regularizing]] [[integral]]s in the evaluation of Feynman diagrams; it assigns values to them that are [[meromorphic function]]s of an auxiliary complex parameter {{mvar|d}}, called the dimension. Dimensional regularization writes a [[Feynman integral]] as an integral depending on the spacetime dimension {{mvar|d}} and spacetime points.