Skip to the Main Content

Note:These pages make extensive use of the latest XHTML and CSS Standards. They ought to look great in any standards-compliant modern browser. Unfortunately, they will probably look horrible in older browsers, like Netscape 4.x and IE 4.x. Moreover, many posts use MathML, which is, currently only supported in Mozilla. My best suggestion (and you will thank me when surfing an ever-increasing number of sites on the web which have been crafted to use the new standards) is to upgrade to the latest version of your browser. If that's not possible, consider moving to the Standards-compliant and open-source Mozilla browser.

December 23, 2007

Instiki and Rails 2.0

I upgraded Instiki to Rails 2.0.2. There are many, many changes to Rails, from 1.2.5, which is what Instiki, previously, was based on. At least, for the present, I made the bare minimum of changes in Instiki, required. Even so, one gets a whole raft of improvements, “for free.”

Posted by distler at 9:52 PM | Permalink | Followups (5)

December 13, 2007


The French term, bricoleur, doesn’t have any real equivalent in English. But perhaps a picture would help.

Posted by distler at 11:52 PM | Permalink | Followups (4)

December 12, 2007


The Open Source version of MovableType was released today. Or sort-of. What’s available, currently, are nightly builds of the next release, 4.1.

But, now that there’s something to work with, I guess I have no excuse to procrastinate any further about porting my modifications of MovableType to version 4. I hope to migrate the blogs here on Golem from version 3.35 to 4.1, as soon as I feel I have something reasonably stable. There will be glitches, though, and I ask, in advance, for everyone’s forbearance.

More broadly, I’d like to refactor as many of my modifications as possible into plugins or modules (that was the original plan, anyway), and hopefully get the modifications, that can’t be so-refactored, committed to the MTOS source tree. That way, people, who want to set up an XHTML+MathML+SVG capable blog, will, finally, have a plug-‘n-play Open Source solution.

Anyone, with a modest knowledge of Perl, who’s interested in helping make such a next-generation blogging system a reality, let me know. I could really use the help. And making this a group effort will ensure that the end-product reflects the needs and desires of the community.

Posted by distler at 10:09 AM | Permalink | Followups (17)

December 10, 2007

AdS/CFT and Exceptional SCFTs

I wrote about Argyres and Seiberg’s paper, incorporating the E 6E_6 and E 7E_7 “isolated” 𝒩=2\mathcal{N}=2 SCFTs as ingredients in a proposed S-duality for certain 𝒩=2\mathcal{N}=2 gauge theories. The proposed dualities, then implied predictions for certain quantities in these, heretofore poorly understood, SCFTs.

Aharony and Tschikawa wrote an interesting paper, in which the endeavoured to check these predictions from AdS/CFT.

Posted by distler at 2:44 AM | Permalink | Post a Comment

December 9, 2007

A Little More Group Theory

With a certain reluctance, I wrote a post about Garrett Lisi’s “Theory of Everything,” specifically about Lisi’s claim that he had embedded 3 generations of quarks and leptons in the 248 of E 8E_8.

The purported “Theory of Everything” involved embedding G=SL(2,)×SU(3)×SU(2)×U(1) Y G = SL(2,\mathbb{C})\times SU(3)\times SU(2)\times U(1)_Y in some noncompact form of E 8E_8 (as it turns out, the split real form, E 8(8)E_{8(8)}), such that the 248 contains 3 copies of R=(2,)+(2¯,¯) R = (2, \mathfrak{R}) + (\overline{2}, \overline{\mathfrak{R}}) where \mathfrak{R} is the SU(3)×SU(2)×U(1) YSU(3)\times SU(2)\times U(1)_Y representation (3,2) 1/6+(3¯,1) 2/3+(3¯,1) 1/3+(1,2) 1/2+(1,1) 1 (3,2)_{1/6} + (\overline{3},1)_{-2/3} + (\overline{3},1)_{1/3} + (1,2)_{-1/2} +(1,1)_1 Note that \mathfrak{R} is a complex representation. So RR, though a real representation of GG, is chiral.

I showed that it is impossible to find an embedding of GG, which yields 3 copies of RR, and hence that Lisi’s “Theory of Everything” doesn’t even rise to the level of impressive numerology.

And that’s where I left it, thinking that this would be enough to settle the matter in the mind of anyone with even a modicum of sense. I allowed to slide Lisi’s claim that he “got the first generation right.” After all, what harm could there be, in letting that little bit stand?

Apparently, I was wrong.

So, just so there’s no ambiguity, let me go back and point out that Lisi’s proposed embedding of GG does not even “get the first generation right.”

Posted by distler at 11:17 PM | Permalink | Followups (13)

December 3, 2007

QGP on the Lattice

I was chatting with John Harris, the former spokesman for the STAR Collaboration, a few weeks ago, when he mentioned to me some recent lattice calculations of η/s\eta/s, the ratio of shear viscosity to entropy density, in pure SU(3)SU(3) Yang-Mills.

This sounded really interesting.

The claim-to-fame of AdS/QGP is that it allows you to compute transport coefficients in a strongly-coupled gauge theory, something that lattice techniques are supposed to be no good at.

Most famous of all is the calculation of η/s\eta/s, which is exactly 14π\tfrac{1}{4\pi} in conformally-invariant AdS/CFT backgrounds, and 14π(1+O(1/λ))\tfrac{1}{4\pi}\left(1+O(1/\lambda)\right) in non-conformally-invariant backgrounds (with the leading 1/λ1/\lambda correction being positive). The quark gluon plasma studied at RHIC is the least viscous fluid known to man. STAR reports η/s0.1\eta/s \lesssim 0.1, more than 100 times smaller than that of water.

It would be pretty cool if lattice calculations could reproduce this. So what’s the trick?

Posted by distler at 11:55 PM | Permalink | Followups (8)