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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 I responded that I didn’t see how it could possibly be worthwhile to publish a “refutation” of an unpublished work.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.
May 26, 2009
Adams Operations
The Adams operations in K-theory are supposed to be defined by three properties
- is a ring-homomorphism.
- .
- Acting on a line bundle, , .
Between that, and the splitting principle, one is supposed to be able to crank them out, explicitly, whenever one needs them.
That’s a pain.
May 25, 2009
α to Ω
There’s been much fanfare about the debut of Wolfram α. While it’s impressive, on a technical level, I think Harvey Ω yields consistently more useful search results.
To each his own.
March 2, 2009
Fun (With) Video
Been rather busy with other matters, but I thought I would share a cool little physics video with you.
February 5, 2009
Temptations of Mathematical Structures
Urs Schreiber:
I find that plenty of people are studying plenty of structures with great enthusiasm whose whose true origin and meaning is clearly unknown. I find this eerie, too, but maybe in a different sense: it’s not so hard to just fiddle around with structures and study axiom systems. What is harder is finding out where these naturally live.
When I was a sophomore at Harvard, I took the Mathematical Methods in Physics course. The syllabus in the printed course catalogue contained a long list of interesting topics to be covered, including “Milbert Spaces.”
On the first day of class, the professor gave an overview of what he planned to cover for the semester. When he got to the aformentioned topic, he said
As pure Math, the theory of Milbert Spaces is really fascinating. But, it turns out, what’s relevant to Quantum Mechanics is the theory of Hilbert Spaces. So that’s what we’ll do, instead…
February 4, 2009
Takeover
Two years ago, I decided to adapt a well-know Rails-based wiki to my nefarious purposes. Twenty five months and 350 commits later, my fork of Instiki had diverged markedly from the original.
This was a source of considerable confusion. If, say, you searched for instiki, my site would show up in the first page of results. But the other, now radically-outdated, application would show up first. Perhaps I should have chosen to change the name.
Or perhaps not.
If you wander over to the main Instiki website, and scroll to the bottom of the page, you’ll notice something curious. It’s running my version of Instiki.
After some discussions, the current maintainer, Matthias Tarasiewicz, decided to adopt my branch (lock, stock and barrel) as the next version of Instiki.
The main Instiki Source Repository has moved to Github (yay!) and mirrors1 mine. The, soon-to-be released, “next” version of the main line of Instiki will be my Version 0.16.2.
My branch is now at Version 0.16.3, based on the latest Rails 2.3.0RC1. One cool new feature is that it automatically chooses between Mongrel (if available) and WEBrick (if not). You just type
./instiki --daemon
and it will automatically select the best available webserver to use.
You’ll always be able to get the latest and greatest version from my site. But, hopefully, releases of the main line of Instiki will never again lag too far behind.
1 One really annoying feature of Git is that it ignores empty directories in commits. Why do people put up with that? There are a bunch of such directories in Instiki (and, indeed, in most Rails apps), so Git seems particularly ill-suited as a source repository for such projects.
January 23, 2009
Lurie II
Jacob Lurie continued his series of lectures with a romp through higher category theory.
January 21, 2009
New beginnings
Today was my first lecture of the new semester, there was some sort of hubbub on The Mall in Washington, and Jacob Lurie gave the first of a series of lectures on “Extended” Topological Quantum Field Theory and a proof of (some might say a precise statement of) the Baez-Dolan Cobordism Hypothesis.
January 20, 2009
Instiki News
As you probably noticed, I took a vacation from blogging to devote my online time to working on Instiki. I’ve made 82 commits to the source repository since my last post on the subject. Much of the motivation came from helping the n-Category Café folks set up their long-promised Wiki.