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November 4, 2009
MathML in Webkit
There was a discussion about displaying math on the web, over at Terry Tao’s blog. It was a little disheartening to learn where most peoples’ heads are at, in that regard. Many seems to be excited at the mere prospect of creating a web service that would turn TeX equations into pictures. Such services are not exactly thin on the ground, I retorted, but hardly satisfactory, either. Fortunately, an actual blind user showed up to explain at least one reason why that wasn’t the answer.
Still, being told, “You should use MathML.” is like being told, “Eat your vegetables.” and is just about as likely to be heeded.
One objection is the lack of browser support, which – these days – means that neither Opera, nor Webkit browsers (Safari, Chrome, …) support MathML. The latter, however, seems to be changing. There’s a plan and, more importantly, there’s actually been code checked into trunk.
Of course, it’s far too early to expect anything usable, but if Alex wants to prioritize, here’s a table of MathML elements and attributes used by itex2MML. Things that aren’t yet supported by his patches are marked in bold.
October 31, 2009
@Font-face
I decided to to dabble a bit with CSS3’s @font-face directive. Downloadable fonts are now supported by all major browsers, so I replaced Georgia (which I never really liked) with Charis SIL as the typeface for running text on this blog.
October 6, 2009
JHEP3
On a completely unrelated note, why is the JHEP3.cls class so broken?
(To amplify a bit, it seems to be incompatible with a number of standard LaTeX packages; some by happenstance, some because it clumsily – and unsuccessfully – tries to emulate them.)
Perhaps there will be a silver lining to the Springer purchase.
October 5, 2009
Fun with (i)tex
Doubtless, you’re familiar with TeX’s \rlap{} and \llap{} commands. They collapse the bounding box of their content to zero width. The content sticks out of the bounding box (respectively, to the right, or to the left), overlapping the surrounding content. Hence the name…
If, however, you take a look at the code for these commands,
\def\llap#1{\hbox to0pt{\hss#1}}
\def\rlap#1{\hbox to0pt{#1\hss}}
you notice one unfortunate thing: they don’t work in math mode. That’s a bummer, because they have (or would have) many useful roles in math mode.
In fact, you might even want a \clap{} command, which would collapse the bounding box to zero width, but cause the content to be centered (sticking out equally, both to the left and to the right) about the current point … something like
\def\clap#1{\hbox to0pt{\hss#1\hss}}
But, of course, that doesn’t work in math mode, either.
Recently, I happened upon this TUGboat article by Alexander Perlis. It explains how to define macros, \mathrlap{}, \mathllap{} and \mathclap{}, which do the same thing as their horizontal mode counterparts, above, but work in math mode.
And I figured out how to implement the same functionality in MathML.
September 18, 2009
Surface Waves
In the comments to my previous post, Thomas Schaefer suggested that I look at the same issue (of the energy density having a linear term, rather than being quadratic in the amplitude of the wave) for the case of surface waves. I don’t think that’s actually the case.
But surface waves are the simplest example I know where one obtains a (highly) nontrivial dispersion relation from relatively simple physics. So it’s fun to review them, anyway.
September 16, 2009
The Sound of One Physicist Wailing
One of the delights of teaching elementary physics is discovering some basic thing that you thought you understood, but actually didn’t. Usually, this occurs late at night, while preparing your lecture for the next morning. And you wonder whether you’ll be able to keep a straight face, the next morning, as you say words you’re no longer quite so sure are true.
I’ve been teaching about waves in a non-technical course. One of the points I like to emphasize is that the energy density, or the intensity, of the wave is quadratic in the amplitude. There are lots of examples of that, with which you are doubtless familiar: electromagnetic waves, transverse waves on a stretched string, …
But we’re studying sound, now. So I thought I would reassure myself that the same is true of sound waves …
August 6, 2009
Spires
If you’re like me, you have a folder on your HD filled with thousands of PDF files that you’ve downloaded, over the years, from the arXivs.
Yuji Tachikawa has written a neat little application, called spires, to manage those PDFs. It serves as a Site-Specific Browser for Spires and for the latest papers on hep-th/hep-ph. It keeps a database of those files you’ve already downloaded. If the paper you want is already downloaded, it will open the local copy. If you don’t have it, or if there’s an updated version at the arXivs, it will prompt you to download the arXiv version.
Here’s a movie of the application in operation. If you want to play with the source code, Yuji’s put it in BZR, which you can browse here.
Hopefully, there will be a few people, in our community, who’ll be interested in developing it further (I’m looking at you, Wolfgang!).
July 10, 2009
Musical Interlude II
Time for another peak into the contents of my iPod.
June 20, 2009
Instiki 0.17
We’ve just released Instiki 0.17, with a number of interesting new features, and a ton of bug fixes.
Among the new features,
- Ability to rename pages
Ability to redirect Wikilinks, using
[[!redirect …]]
- HTTP 301 redirects, for redirected/renamed pages
I should like to thank Json Blevins, Ari Stern, and the crew at ncatlab.org for their feedback, bug reports, and remorseless testing. I wouldn’t (indeed, couldn’t) have done it without them.
June 19, 2009
Synchronicity
I was visiting the University of Michigan earlier this Spring, where Gordy Kane told me a story. He’d recently given a public lecture, and was somewhat taken aback when, during the question period afterwards, he was asked about the status of Garrett Lisi’s Theory of Everything. The questioner was convinced that Lisi was a key player in the unification 'biz, and was surprised that his theory had not received more attention (which is to say, had not been mentioned at all) in Gordy’s talk.
The very same day, I received an email from a mathematician working in Representation Theory. He was disgruntled that his student was being asked about Lisi’s work in the course of job interviews. He knew I had some blog posts about Lisi’s “theory”, but had I written these up anywhere? I responded that I didn’t see how it could possibly be worthwhile to publish a “refutation” of an unpublished work. And, in any case, what I had done was of such a mind-numbingly trivial nature that no respectable journal (in either Math or Physics) would consent to publish it. But Skip insisted that it would be helpful to someone like his student to be able to cite a paper in which this stuff had been debunked.
By coincidence, an exchange of comments, with the man himself, at the at the n-Category Café, convinced me that my blog posts have been less than efficacious.
So I decided to take Skip up on his suggestion and try to distil the arguments of the aforementioned blog posts and strengthen them into a theorem that some (not necessarily self-respecting) Math journal might publish.
June 18, 2009
When in Rome …
Anyone up for dinner Saturday night?
I’m staying a few blocks west of Termini. I may be a bit jetlagged, but promise witty repartee, to the extent I am able.
Akulov-Volkov Redux
One of the least penetrable chapters of Wess & Bagger is the chapter on nonlinear realizations of supersymmetry, AKA the Akulov-Volkov formalism. Nati Seiberg gave a lecture (based on joint work with Zohar Komargodski) about a new approach to the subject, which seems much simpler. Of course, anything he can do should also be possible in the AV formalism. But many things are much more transparent in his formalism than in theirs.
June 17, 2009
Penrose Diagram Follies
Gary Horowitz gave a beautiful talk, on Tuesday, about his work with Evan and Albion on a holographic model of blackhole formation and evaporation in AdS.
It’s a very nice paper, which discusses a 5-dimensional generalization of BTZ blackholes, which can be studied (seemingly reliably), in AdS/CFT.
But I got somewhat annoyed when he he threw up a slide of figure 4 in their paper
June 9, 2009
Draining the Swampland
Vijay Kumar and Wati Taylor have an interesting paper out, in which they argue that all anomaly-free supersymmetric field theories, coupled to 6D supergravity, can be UV-completed in string theory. Well … umh … that’s a bit of a stretch, but, morally, that’s what they claim.
May 31, 2009
Musical Interlude
Here’s a sample of some of the music that’s getting heavy roation on my iPod, these days.