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Agent of change
January 31, 2003
Bombshell
We’ve all seen the gruesome pictures of the Iraqi Kurds, gassed in March 1988 in the town of Halabja near the Iranian border. Proof positive (as reiterated in the State of the Union address this Tuesday evening) that Saddam is an evil tyrant, who would “gas his own people.”
There’s no doubt that Saddam is an evil tyrant.
But, according to Stephen Pelletiere, who is very much in a position to know, it is overwhelmingly likely that it was the Iranians, not the Iraqis, who gassed the Kurds of Halabja.
And the President surely knows this (assuming he wasn’t too busy throwing spitballs during the relevant briefing).
So what was he talking about on Tuesday?
Update: Pelletiere’s conclusions have been hotly disputed in many quarters. HumanRightsWatch concluded that it was mustard gas and sarin, which the Iraqis did possess, which killed the inhabitants of Halabja. (The main pillar of Pelletiere’s argument is that hydrogen cyanide — supposedly part of the Iranian, but not Iraqi, arsenal at the time — was used in the attack.) And, even if Pelletiere is right about Halabja, it is almost certain that Saddam’s subsequent murderous campaign against the Kurds included the use of poison gas against other — less famous — targets.
This is an important point: the Administration is not arguing that we should go to war because Saddam killed 100,000 Kurds. The argument (which, when stated plainly, may sound a little callous) is that we should do so because he used WMDs (poison gas) to kill some fraction of them. So “details,” like what exactly happened in Halabja, matter.
January 30, 2003
Render Onto …
So I’m not all that please at how my last post renders on the Mac (Mach-O Mozilla with the Mathematica Fonts). The “stretchy” characters (the integral sign and the overbar on the anti-D3 branes) … aren’t.
How does it look on other platforms?
Anyone using one of the MathML plugins for (gasp, shudder) Internet Explorer?
On another matter, you might have noticed that the RSS feed for Brad DeLong’s blog has disappeared. For the second time in a week, the RSS parser is choking, because his feed contains “undefined entities” ( this time; last time it was £). These are perfectly valid in XHTML, but must not appear in an RSS feed, for it to be valid XML. I think it’s fine to use their numerical equivalents (  and £, respectively). Or you can wrap the whole <description> as CDATA. Or maybe I need a yet-more-liberal parser.
Anyway, in a day or two, Brad will have posted enough new stuff for the offending article to slip off his feed, and then we should be good for another week.
Update: Actually, Brad’s problem comes down to his using faulty old templates to generate his RSS feed. The new MT Templates don’t have these problems.
Long Live de Sitter!
(Warning! This post uses MathML. The equations will probably look like garbage unless you are viewing it in Mozilla, with the requisite fonts installed. Sorry, that’s just life.)
Kachru et al suggest a way to obtain classically-stable (and quantum-mechanically long-lived) 4D de Sitter solutions of string theory.
The starting point is the class of compactifications introduced by Giddings et al. There, the flux-induced superpotential,
fixes the string coupling and the complex structure of the 3-fold , leaving the Kahler modulus, (we’ll assume only one) as a flat direction.
The next stage (a bit of handwaving, but not implausible) is to assume that nonperturbative effects induce a superpotential for which lifts this remaining flat direction. In a fairly robust fashion, one ends up with a supersymmetric vacuum in 4D anti-de Sitter space.
Now comes the tricky step. We imagine changing the fluxes (a discrete choice) so that the tadpole cancellation condition now requires the presence of one (or a small number of) brane(s). This breaks supersymmetry and induces a term in the potential which would normally lead to a runaway behaviour for . Naively, I might guess that the coefficient of this term would be large, and that it would totally overwhelm the nonperturbative superpotential which generated a minimum for in the first place.
Well, not according to these guys. They claim that the coefficient can be small (so as not to totally destabilize the minimum) and, moreover, can be fine-tuned (again, we have only discrete choices) to produce a minimum with a small (tiny!) positive cosmological constant.
If you swallow all of this, it’s not to hard to believe the last step: namely, while this minimum is only metastable (we still have for , after all), it can be incredibly long-lived — more than