# wordpress and latex.

i was thinking on using latex in maybe some blog entries, maybe here or maybe somewhere else. so i decided to see what existing plugins there are. after a bit of searching, i stumbled over wp-latex, which is apparently also used by wordpress.com. unfortunately, it has a kind of clumsy syntax (“$latex formula$” instead of simply “$formula$”). and it has no support for display style formulae, i.e. something centered in its own line, as opposed to inline formulae which try to fit neatly into the text.

so i tried to fix that. and it worked out, and i can still use a “normal” $by appending a blackslash in front of it. well, euler's identity is , as simple as that. if you want to see something more complicated: let be a number field or an algebraic function field. then, we have the following commutative diagram with exact rows and columns: here, simply denotes the cokernel of the map which assigns to every unit its principal divisor ; in particular, . finally, denotes the cokernel of the degree map , where in the number field case, , and in the function field case, . this is written as follows:  1let \$K\$be a number field or an algebraic function field. then, 2we have the following commutative diagram with exact rows and 3columns: 4\$\$\xymatrix{ & 0 \ar[d] & 0 \ar[d] & 0 \ar[d] & \\ 0 \ar[r] & 5\calO^* / k^* \ar[r] \ar[d] & \Div^0_\infty(K) \ar[r] \ar[d] & 6T \ar[r] \ar[d] & 0 \\ 0 \ar[r] & K^* / k^* \ar[r] \ar[d] & 7\Div^0(K) \ar[r] \ar[d] & \Pic^0(K) \ar[r] \ar[d] & 0 \\ 0 \ar[r] 8& K^* / \calO^* \ar[r] \ar[d] & \Id(\calO) \ar[r] \ar[d] & 9\Pic(\calO) \ar[r] \ar[d] & 0 \\ & 0 & H \ar@{=}[r] \ar[d] & H 10\ar[d] & \\ & & 0 & 0 & }\$\$11here, \$T\$simply denotes the cokernel of the map \$\calO^* \to
12\Div^0_\infty(K)\$which assigns to every unit \$\varepsilon \in
13\calO^*\$its principal divisor \$(\varepsilon)\$; in particular, 14\$T \cong \Div^0_\infty(K) / (\Princ(K) \cap \Div^0_\infty(K))\$. 15finally, \$H\$denotes the cokernel of the degree map \$\Div(K) \to
16\G\$, where in the number field case, \$\G = \R\$, and in the 17function field case, \$\G = \Z\.  note that this example also shows a problem: namely, the vertical alignment of the inline formulae sucks bigtime. let's see how to fix this... posted in: math www tags: places: ## comments. wrote on february 28, 2009 at 22:06: oh, and the formulae graphics are not transparent. well, maybe i’ll try to fix that later… wrote on february 28, 2009 at 22:40: also, it is very strange to read the entry in a feed reader using black fonts on white background instead of the other way around in your blog. the diagram is okay, but the in-line formulas are hardly readable. wrote on march 1, 2009 at 00:12: that’s true, but feed readers screw up most things anyway which are not plain text. so why care? ;) well, one possibility is to modify the latex plugin to return different code (namely: links to others pictures) in case the test is requested for a feed and not for displaying on the site itself. i don’t know what’s the best way to solve this in wordpress… wrote on march 1, 2009 at 01:01: well, that’s changed. was easier than i thought to change, the hardest part was testing whether it really changed. wrote on may 4, 2009 at 01:41: i just upgraded the wp-latex package and put my own modifications mostly into an own plugin. now also formulae in comments should work, likee^{i t} = \cos t + i \sin t\$.

wrote on may 4, 2009 at 01:46:

note that the formulae now have transparent background, whence they probably suck if your feed reader shows the pngs on black background :)

wrote on may 4, 2009 at 05:52:

[...] which interest me, for example things related to my research. the formulae will be rendered with latex; mathml is simply unuseable so far. an example post shows a feature with i added to my wp-latex [...]

wrote on may 5, 2009 at 02:51:

another update. i added support for align* math environments to the latex plugin. this required hacking the latex renderer part of the wp-latex plugin; i just did that for the dvipng part. in case anyone is interested in my version of the plugin (including my wrapper plugin), contact me.