Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!zodiac!saturn!xanthian
From: xanthian@saturn.ADS.COM (Metafont Consultant Account)
Newsgroups: comp.text
Subject: Re: Feynman diagrams in LaTeX
Message-ID: <10237@zodiac.ADS.COM>
Date: 30 Dec 89 09:02:14 GMT
References: <300@nbivax.nbi.dk>
Sender: news@zodiac.ADS.COM
Organization: Advanced Decision Systems, Mt. View, CA (415) 960-7300
Lines: 59

In article <300@nbivax.nbi.dk> pmunck@nbivax.nbi.dk (Peter Munck) writes:
>I have produced a lot of Feynman diagrams using the LaTeX figure environment,
>but there a certain types of diagrams that I cannot figure out how to produce.
>The difficult diagrams are those radiative correction diagrams where a photon
>or a gluon are emitted and absorbed at the same fermion line. Has anyone out
>there produced such diagrams ?
>For those not familiar with Feynman diagrams I can describe what sort of
>picture I'd like :
>I'd like to produce a spiral curved in a half arc, or similarly a (sine)wave
>curved in a half arc. The spirals and waves are easy to produce along a straight
>line, but if you want to curve them it's really something else.
>I'd be pleased with any respond.
>
>        Peter Munck
>        University of Copenhagen
>        The Niels Bohr Institute
>        Blegdamsvej 17
>        DK-2100 Copenhagen O
>
>        PMUNCK@NBIVAX.NBI.DK


Well, if the curved "spirals" (I cannot visualize what that means;
helicies perhaps?) and sine waves are needed in a limited number of
sizes and orientations, one solution would be to create them as
symbols using METAFONT, and to include them at the desired point in
the diagram using the text option of the picture environment as
detailed on page 104 of the paperback LaTeX manual.  Designing a
METAFONT symbol for a sine wave along a half circular arc, at least,
should be a piece of cake, as should be instancing it at orientations
of, say, multiples of 15 degrees to make a font of bent sine wave
"characters".  If the 45 degree instance is character code #3 in your
bent sine font bsf30.300pk of size 30 points for use on a 300dpi
device, then

	\put{2.3,5}{\bentsinefont\char 3}

should put its lower left corner at location (2.5,3), where

	\font\bentsinefont=bsf30 at 30truepts

or some such definition occurs earlier in the document or in an
included header/style file.  It shouldn't be too awful a limitation to
pick an angle for the line it is supposed to join so that both ends
of the bent sine wave match the line nicely.

--
Again, my opinion, not the account furnishers'.

xanthian@well.sf.ca.us
Kent, the (bionic) man from xanth, now available as a build-a-xanthian
kit at better toy stores near you.  Warning - some parts are fragile.

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