# Feyn font

A package of fonts for displaying Feynman diagrams.

Version 0.4.1, 2017 November 03.

Persistent URL: http://purl.org/nxg/dist/feyn

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.

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]

## Licence

This software is copyright 1991, 1994, 2001-2, 2005, 2008-17, Norman Gray.. It is distributed under the terms of the 2-clause BSD Licence.

## History

Version 0.4.1, 2017 November 3

The package is now licensed under the terms of the 2-clause BSD licence.

The only other changes from v0.4b2 are mild documentation adjustments (sorry for the long delay between 0.4b2 and 0.4).

Version 0.4 was not widely released.

Version 0.4b3, 2013 April 12
• Changed \below to \belowl, and added companion \belowr.
Version 0.4b2, 2011 April 9

As for version 0.4b1, but with the addition of aV for a backward arrow (rarely used, but included for consistency; thanks to Thomas Pruschke for the suggestion). Also added: flo for the closed fermion loop, for phi^4 theory (plus floV and floA for completeness; thanks to Hoang Nghia Nguyen for the suggestion; the font should now be able to produce all scalar theory diagrams).

Version 0.4b1, 2010 January 23

Addition of the extended-size `feynx' fonts, and the \FEYN macro (thanks to Luciano Pandola for the suggestion).

Adjustments to the sizing of half-loops (the half-loops are now squashed, though the quarter-loops aren't). Added ghost loops; we can now do all the diagrams of 2-loop QCD. The quarter-loop gluons now taper at both ends, so that two quarter-loops are no longer the same as one half-loop.

...
Earlier release notes are available

The nominal distribution point for the Feyn package is CTAN, under fonts/feyn.

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

Since the package is on CTAN, it should be easily installed and updated using the tools which support this in your TeX distribution. For TeXLive, that's tlmgr, and for MikTeX see the maintenance section of the manual.

### Doing the installation by hand

...how thoroughly old-skool of you!