# Feyn font

A package of fonts for displaying Feynman diagrams.

Version 0.3.3, 2009 October 8.

• Canonical URL: `https://purl.org/nxg/dist/feyn`
• Repository: browse, hg clone URI

This package is intended to produce relatively simple Feynman diagrams, primarily for use within equations.

This package differs from Thorsten Ohl’s `feynmf/feynmp` package (at CTAN, or see the TeX FAQ). FeynMP works by creating Metafont or MetaPost figures using a preprocessor. It’s more general than this package, but is at its best when creating relatively large diagrams, for figures. In contrast, the present system consists of a carefully-designed font with which you can easily write simple diagrams, within equations or within text, in a size matching the surrounding text size.

The propagators and vertices which are implemented are those which seem to appear most often in non-figure displays (the practical definition of ‘appear most often’ is ‘which I wanted’ and ‘which people asked me for’). I have no current plans to extend the package further, but I’m willing add other features if you can make a case for them.

The package is on CTAN, and is included in TeXLive but not, as far as I’m aware, teTeX. The arXiv started using TeXLive 2008 in summer 2008, so it should be available there from that date.

There is further documentation, plus numerous examples, in the package documentation.

[By the way, I have little idea of how many people actually use this package. If you do use it, I’d be most grateful if you could drop me a line just to say so]

## History

Version 0.3.3, 2009 October 8
Minor documentation improvements.
Version 0.3.2, 2009 August 5
Minor documentation improvements – no functional difference from 0.3.1
Version 0.3.1, 2008 February 29
No changes from 0.3b3
Version 0.3b3, 2008 January 30
This time it works properly, with the ‘globalbang’ mechanism fixed (thanks again to Bryan Chen’s patience).
Version 0.3b2, 2008 January 27
Now works properly with amsmath package, as long as it’s loaded second (and the `{no,}globalbang` options have been added to force behaviour when necessary). Thanks to Bryan Chen for the bugreport.
Version 0.3b1, 2008 January 17
Added small fermion loops (including inverted, and arrowed); added a variant of the proper vertex which is all-black rather than hatched (both these suggestions from Bryan Chen). Some documentation improvements.
Version 0.2-2, 2005 December 2
It turned out that the `.dtx` documentation wasn’t generated properly when called in the not-terribly-useful `\AlsoImplementation` mode; fixed, and that mode is no longer the default.
Version 0.2-1, 2005 December 2
Doh! The new files `feyn18.mf`, `feyn24.mf` and their textsize counterparts were not included in the 0.2 distribution; thanks to Purnendu Chakraborty from the Saha Institute for discovering this. This release also includes fixed gluon loop characters: they were all 1 module high before, but now have the correct sizes.
Version 0.2, 2005 March 24
Substantial restructuring. Most particularly, (almost) all of the propagators now have versions with arrows integrated into the character, and each of the characters has an ‘annotation point’ defined, and accessed using the `\momentum` macro, or the ‘!’ abbreviation. This makes the ‘a’ character (the arrow) largely redundant and the `\vertexlabel` macro rather less important.
Version 0.1, 1991, 1994, 2001
Initial version. The font was first produced in 1991 or so, first released in 1994, and tidied up and more carefully re-released as version 0.1 in 2001.

Version 0.3.1 of the feyn package is included in the TeXLive 2008 distribution, so you may have it on your machine already. If not, or if you need a more up-to-date version, read on.

It’s also at CTAN, in /tex-archive/fonts/feyn/

Installation is much as usual.

2. Run LaTeX on the file `feyn.ins` – this will unpack the style file `feyn.sty` amongst other files. Place this ‘somewhere where TeX can find it’. Similarly, place the `.mf` files somewhere where the font-generation mechanism for your platform can find them. For example, in the TeXLive distribution, the feyn `*.mf` files appear in the directory `/usr/local/texlive/2008/texmf-dist/fonts/source/public/feyn/` and the `feyn.sty` file in `/usr/local/texlive/2008/texmf-dist/tex/latex/feyn/feyn.sty`, so that if I were installing them ‘privately’, I would put them in `/usr/local/texlive/texmf-local/fonts/source/local/feyn/` and `/usr/local/texlive/texmf-local/tex/latex/feyn/feyn.sty`. With the teTeX and TeXLive Unix distributions, the output of `kpsepath mf` shows the list of places where TeX will look for Metafont source files. The font files should be generated on the fly when you first refer to them. See also the relevant discussion in the TeX FAQ about ‘where LaTeX can find them’.
3. Run LaTeX on the file `feyn.dtx` to obtain the documentation, which is prebuilt in `feyn.pdf` (this should generate the font files as a side-effect).