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December 31, 2009
Haiku
As part of his science fair project, my 3rd-grader needed a large number of random strings of 8 digits, in each of which “1” appears four times, and “2”–“5” appear once each.
December 28, 2009
Instiki 0.18
I just released Instiki 0.18.
It’s been half a year, since I announced the release of 0.17 and there’s lots of new stuff. So I guess it’s time for an upgrade …
New feature include:
- Syntax colouring for code blocks: ‘
html’, ‘xml’, ‘ruby’, ‘ansic’, ‘javascript’, ‘sqlite’, ‘yaml’ and ‘css’ modes. - Source view [suggested by Andrew Stacey]
- Auto-resizing Textareas scale to fit viewing area.
- Passenger support (including X-Sendfile support, if the Apache
mod_xsendfilemodule is installed). - Upgraded to Rails 2.3.5 and Rack 1.1.
- Now runs on Ruby 1.9. (If you’re a Passenger user, you may need to upgrade to Passenger 2.2.8, which works around some bugs in Ruby 1.9.1.)
- Upgraded for itex2MML 1.3.19 (which works under Ruby 1.9, and has several new features, relative to 1.3.15).
and a boatload of bugfixes.
Update (1/7/2010):
Because of some character encoding issues under Ruby 1.9 (mostly affecting My SQL users), I decided to issue a quick update to Instiki 0.18.1. [Thanks to Andrew Stacey for running these issues down.] I also added some new features: (Markdown-Extra-style) fenced code-blocks and ‘fortran’ syntax colouring. [Both courtesy of Jason Blevins.]Please
rake upgrade_instiki
before running the new version.
December 21, 2009
GraviGUT
One of the disadvantages of having waded into the Lisi affair is that I keep getting asked about related ill-conceived ideas for “theories of everything.” For the most-part, such ideas don’t have a relentless publicity machine behind them. Nor do they receive what can only be described as a credulous reception in certain corners of the Mathematics community. But still, it is assumed that one has an opinion about them.
One such idea is the “GraviGUT” of Nesti and Percacci. The bosonic fields consist of a connection for a noncompact gauge group, and a 1-form, , transforming in the 14-dimensional vector representation. More formally, we assume that is a principal bundle, and a vector bundle, associated associated to via the 14-dimensional vector representation. The fields consist of a connection on , and a 1-form, , with values in sections of .
December 20, 2009
MarsEdit
For many years, I was an enthusiastic user of ecto. Unfortunately, Adriaan gradually lost interest, and ecto3 languished – seemingly forever – as bug-ridden, user-unfriendly, beta software. Eventually, he sold it to illuminex, where it continues to languish (though I think they’re actually trying to charge people for using buggy, user-unfriendly beta software).
Anyway, to make a long story short, I’ve switched to MarsEdit, which – unlike ecto3 – is not the least bit painful to use.
To celebrate, I created some MarsEdit TextFilters.
December 14, 2009
So Much For the Concept of “Tree Graph”
Topology meets botany.
December 8, 2009
Wave
I’ve been playing around with Google Wave, and the Oxyxy Gadget.
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.