## February 26, 2007

### XSS

#### Update (5/25/2007):

Sam Ruby ported this Sanitizer to HTML5lib. For most purposes, that’s a much more robust foundation, so all my future efforts will be devoted to the HTML5lib version.Files:

Rudimentary documentation is available.

The original version of the Sanitizer, described in this post, can be found here.

What free time which might, otherwise, have been devoted to blogging last week, was devoted to another matter.

On Monday, I discovered that Instiki, including my MathML-enabled branch, was vulnerable to Cross-Site Scripting (XSS). That is, visitors to an Instiki Wiki could inject malicious javascript code onto your page.

## February 18, 2007

## February 17, 2007

## February 15, 2007

### Instiki Update

I’m now running several Instiki wikis, for various projects. I’ve also been very busy fixing things under the hood and I’m quite pleased with the result. Since I’ve gotten several inquiries about MathML-enabled Wiki software, and this branch of Instiki finally feels like it’s ready for primetime, the project now has its own website.

More technical details below the fold.

## February 13, 2007

### Primer

I’ve been reading Michael Dine’s new book, Supersymmetry and String Theory: *Beyond the Standard Model*.

Since any one of the phrases in the title could well be (and has been) the subject of a multi-volume opus, it comes as somewhat of a surprise that the entire book weighs in at a mere 503 pages.

This gives, in places, a whirlwind feel to the book. An extreme example is the chapter on General Relativity. In 15 pages, Dine introduces general coordinate transformations, derives the Christoffel symbols, discusses the Riemann curvature tensor and its symmetries, derives the Schwarzschild solution as the most general static, isotropic solution to the vacuum Einstein equations, introduces Bekenstein and Hawkings results on the thermodynamics of blackholes, and still has a page left over to discuss the coupling of spinors to gravity.

Another more minor example is his discussion of Grand Unification. He correctly notes that unification works better with supersymmetry than without it. To drive home the point, he presents non-supersymmetric Grand Unification in the maximally unflattering light (run $\alpha_1,\alpha_2$ up to the point where they unify, then run $\alpha_3$ down to the $Z$ mass, where it is 7 orders of magnitude off). The naïve reader might be forgiven for wondering why anyone ever thought of non-supersymmetric Grand Unification in the first place.

But these are minor quibbles. My only real complaint is that this book stops just short of where someone with an interest in String Theory and beyond-the-Standard Model physics would like to be taken. I think that one would want, in such a book, a discussion of the leading candidates for bridging the gap: heterotic M-theory and Type-IIB orientifolds with fluxes.

These get very brief mention (respectively, in section 28.7, where it is explained that heterotic M-theory solves the “Dine-Seiberg problem,” and in the “Coda,” where we are introduced to the “landscape”), But the presentation of Randall-Sundrum, in chapter 29, would be much improved by an explanation of the warped nature of the typical heterotic M-theory and, even moreso, by a mention of the large warpings that can arise in IIB flux compactifications. More generally, a discussion of these contemporary efforts at string phenomenology would provide an opportunity to tie the last part of the book more closely together with the considerations of the first 300 pages.

Still, there’s a wealth of information here, for the beginning graduate student (a solid course in Field Theory, and a rudimentary acquaintance with the Standard Model are a prerequisite), and nuggets of insight that will satisfy the seasoned researcher. The chapters on supersymmetry and cosmology are especially good.

I would say that this book belongs on the bookshelf of any (aspiring) high energy theorist. But perhaps the bedside table would be an even better location.

## February 6, 2007

### Tensor Modes

How strong are the tensor mode fluctuations produced by inflation? We don’t know yet, because they haven’t yet been seen. But satellites now in planning (which might even get built if NASA recovers from the Presidential foolishness about sending men to the moon and to mars) will measure the ratio $r = \frac{P_t}{P_s}$ of power in the tensor modes to the power in scalar modes to an accuracy of around $r\sim {10}^{-2}$.

What would it mean if they actually see something? Liam McAllister is visiting us, and gave a lovely talk about the implications for string theory.