Musings

One of the things about a new medium is that it will almost inevitably find new, unanticipated, uses. I’m excited about the MathML-enabled weblog as a medium for physics research. How exactly that will pan out remains to be seen, but over at the String Coffee Table, Urs Schreiber is trying an experiment.

Back in medieval times, when you were preparing a paper, you might mail paper copies of a draft version to your friends to get some comments. In modern times, you might email those same friends a PDF file. Whichever the medium, the distribution-list is necessarily limited.

Urs is working on a paper. Hoping for feedback from a wider audience than he could get by (e)mailing around a draft, he has posted parts I and II to the weblog. So head on over, read his draft, and give him some feedback.

(Posted via WiFi from San Jose International Airport, using a beta version of Ecto, the successor to Kung-Log.)

A quite frightening story about the increasing sophistication of spammer/crackers [tip 'o the hat to Gary F]. It’s been clear for a while that spammers have crossed the line into computer cracking — using hijacked Windoze boxes to distribute spam and mount DDoS attacks on anti-spam sites. What’s new here is the sophistication of the attack, and the target — a linux system running GeekLog, a popular PHP-based weblogging program.

Cracking into a Windoze box carries very little risk of detection, much less of being tracked down. Windoze users are inured to the thought of their machine being compromised by viruses, spyware, etc. and they have relatively few forensic tools available for tracking down their attacker. Linux users are, by and large, a more sophisticated bunch, raising the stakes for a potential attacker.

I guess this is all the more reason to keep your software up to date, which includes upgrading MovableType to 2.65, plugging a hole in lib/MT/XMLRPCServer.pm.

Yet another update to Henrik Gemal’s acronym plugin for MovableType, meaning yet another update to my patch, which offers improved handling of acronyms and abbreviations.

Update (12/28/2003): I’ve posted a new version of the patch, fixing a few things which seem to have been broken by the new logic in version 0.6 of Gemal’s plugin. This should fully restore the functionality to that of previous version of my patched plugin.

Update (2/13/2004):Yet another update to my patch to bring it into line with version 0.7 of Gemal’s plugin. (Mercifully, my patch get shorter and shorter, as Gemal incorporates more of my changes with each iteration of his plugin.)

Update (5/28/2004):Yet another update to my patch to bring it into line with version 1.0 of Gemal’s plugin. (Which, actually, is functionally identical to 0.7.)

If you’ve been trying to follow the continuing saga of electronic voting machines, as I have, it’s pretty hard to keep track. The scandalous revelations about the operations of the leading manufacturers, like Diebold just keep coming and coming and coming.

Finally, there’s a site dedicated to keeping tabs on the whole affair. It won’t be joining my blogroll any time soon (it’s just too painful to read regularly), but it’s good to know that it’s there…

File a bug report, you dork.

That’s what I shoulda done. I’ve grumbled about the bugs in the rendering of MathML in recent version of Mozilla/MacOSX. Daniel Jamous actually did the legwork, tracked down when the breakage occurred (between 1.3a and 1.3b) and filed a proper bug report. Hopefully, now it will get fixed.

Everyone’s all a-titter about Witten’s latest, which appeared today. He studies Maximal Helicity-Violating amplitudes ($n-2$ gluons of one chirality and $2$ of the other) in perturbative large-N, $\mathcal{N}=4$ Yang-Mills theory. After transforming from momentum space to twistor space, he find that the amplitudes are supported on certain holomorphic curves in twistor space. And he relates this to a computation in the open topological B-model with target space $CP^{3|4}$.

Arvind has a brief summary over at the Table. Me, I’m still wading my way through the 97 page opus.

I’m proud to announce a new blog, The String Coffee Table. It’s a group blog by five young string theorists. They’re all veterans of other public fora, like sci.physics.research, but, except for Aaron, they’re new to blogging.

The new blog is hosted right here on Golem, and the eagle-eyed among you will notice a certain … ah … similarity with Musings. They’re both powered by the same cutting-edge, MathML-enabled technology and, but for the new CSS style-file, they share almost all the same code.

Head on over and check it out…

Thomas Dent’s comment on my previous post reminded me of an anecdote.

Several years ago, I was sitting in the CERN cafeteria, chatting with a phenomenologist colleague. I opined that it was, on balance, a very good thing that the then-recent advances in our understanding strongly-coupled supersymmetric gauge theories had not come a decade earlier. “Why so?” asked my friend. “Because,” I replied, “if we’d known all the stuff in the early '80s, the community would have wasted the intervening decade applying that knowledge to building elaborate models of extended technicolour. Instead, we poured our efforts into developing string theory.” At this, my friend grew very agitated. “But you don’t understand!” he spluttered, “There are so many more possibilities for constructing models now.”

Indeed …

Hitoshi Murayama was in town this week, and gave a talk about some decidedly nonstandard alternatives to the Higgs content of the MSSM. For those too young to remember the early '80s, nothing can fully evoke the horror of hearing the phrase “walking technicolour” again.

But the supersymmetric Fat Higgs model is not your father’s extended technicolour model, as it borrows rather heavily from the work of Seiberg and others on strongly-coupled SUSY gauge dynamics. The motivation, nowadays, is rather different, too. Rather than trying to eschew fundamental scalars (which are implied by supersymmetry anyway), or to provide a solution to the hierarchy problem (why is the Higgs so light?), the idea is to permit the Higgs to be heavier than the constraints of the MSSM would naturally allow.

Speaking of rather exclusive clubs, the dozen or so people who use my utarticle.cls LaTeX class-file may be interested in knowing that there’s a new version out. At Aaron Bergman’s instigation, I’ve “fixed” the \email{} macro. Now, loading the hyperref macro package,

\usepackage[]{hyperref}

converts \email{r.j.drofnats@st.anford.edu} into a clickable mailto hyperlink in the resulting PDF (or DVI) file. It’s a small thing, an arguably really geeky thing, but it makes me happy.

Another MathML-enabled weblog on the block: Bitácora de matemáticas. Antonio Luis Martínez Rico joins a rather exclusive club. Yuan-Chung Cheng’s blog seems to have been abandoned, except by the comment spammers, so the list of MathML-enabled blogs is currently … ahem! … distressingly short.

If you run a website, you may have noticed some “unlikely” entries in your Referer logs, from what are apparently porn sites hoping to appear in your Referer listings, on the off-chance that you publish those somewhere on your website.

What I didn’t realize is that these are apparently being generated by Trojan horses running on some unsuspecting schmoe’s Windoze machine.

Here’s one who’s been visiting me a lot recently. A typical evening’s visit looks like:

bu-wcs2-sand.nipr.mil - - [05/Dec/2003:18:03:52 -0600] "GET /~distler/blog/images/bigthinker.jpg HTTP/1.0" 200 1443 "-" "Mozilla/3.01 (compatible;)"
bu-wcs2-sand.nipr.mil - - [05/Dec/2003:18:03:52 -0600] "GET /~distler/blog/archives/000064.html HTTP/1.0" 200 8793 "http://www.busty2.com/?big_tits" "Mozilla/4.0 (compatible; MSIE 5.5)"
bu-wcs2-sand.nipr.mil - - [05/Dec/2003:18:03:52 -0600] "GET /~distler/blog/ie.js HTTP/1.0" 200 2069 "-" "Mozilla/3.01 (compatible;)"
bu-wcs2-sand.nipr.mil - - [05/Dec/2003:20:44:23 -0600] "GET /~distler/blog/archives/000064.html HTTP/1.0" 200 8793 "http://www.transsexualpalace.com/?trannies" "Mozilla/4.0 (compatible; MSIE 5.5)"
bu-wcs2-sand.nipr.mil - - [05/Dec/2003:20:44:23 -0600] "GET /~distler/blog/images/bigthinker.jpg HTTP/1.0" 200 1443 "-" "Mozilla/3.01 (compatible;)"
bu-wcs2-sand.nipr.mil - - [05/Dec/2003:20:47:01 -0600] "GET /~distler/blog/archives/000165.html HTTP/1.0" 200 19720 "http://www.transsexualpalace.com/?trannies" "Mozilla/4.0 (compatible; MSIE 5.5)"
bu-wcs2-sand.nipr.mil - - [05/Dec/2003:20:47:01 -0600] "GET /~distler/blog/images/MathML.png HTTP/1.0" 200 3238 "-" "Mozilla/3.01 (compatible;)"

Note the different User-Agent and bogus Referer string when the 'bot downloads a token image or javascript file in an attempt to look more “human”.

nipr.mil is the US Military’s web proxy, so we can’t exactly dash off an email of enquiry, but I’m gonna assume that no one is deliberately running a Porno Referer Spambot on a DOD computer. That pretty much leave the Trojan Horse explanation.

Which begs the obvious question: if you’re gonna go to the trouble of planting a Trojan Horse on a milnet computer, isn’t Referer Spam kind of a low-stakes objective?

Apparently, there’s a heap overflow vulnerability in rsync 2.5.6 (the version that ships with Panther) and earlier. This is a serious threat, if you run rsync in daemon mode. Upgrading to 2.5.7 fixes the problem.

Between that and the local root hole in the Linux kernel, Linux folks have been busy lately. (Point of amusement: note the PGP signature on that Advisory!)

Don Marolf was in town this week, and talked about his work with Sorkin on Entropy Bounds. The Bekenstein bound,

on the entropy of an object of energy $E$ and size $R$, ($\alpha$ is some dimensionless number) and the Holographic bound

on the entropy in a region of area $A$ (a more precise formulation of this latter bound is due to Bousso) have been much bruited about since they were proposed.

The validity of these bounds ultimately rests on an argument involving the consistency of the generalized Second Law. Were it possible to have an object which violated one of these bounds, one could either drop it into a blackhole, or accrete matter onto it to form a blackhole and the resulting process would produce a net decrease of the total entropy in the universe.

What Marolf and Sorkin note is that such highly entropic object are necessarily an important component of the Hawking radiation. In a thermal ensemble at temperature $T_{\mathrm{BH}}= (4\pi R_{\mathrm{BH}})^{-1}$, the probablility of finding such an object is proportional to $e^{-\beta F}$, where $F$ is the free energy, $F=E-TS$. Even when the temperature of the blackhole is low, whenever $S$ is large enough to potentially violate one of these bounds, these objects become an important component of the thermal ensemble.

According to their analysis, any process in which — if one neglected the Hawking radiation — the Generalized Second Law would be violated, will either be forbidden or will be accompanied by the emission of enough of these guys in the Hawking radiation that the total entropy increases, and the Second Law is satisfied.

Admittedly, I’ve never been a big fan of Holography as a putative fundamental principle of quantum gravity, but Marolf and Sorkin’s argument seems to have unhitched it from its grounding in the Generalized Second Law. That connection was, heretofore, the main reason for believing in Holography.

Dan Gottesman and John Preskill have a nice little paper which seems to be a quite devastating critique of a recent proposal by Horowitz and Maldacena on blackhole information.

The blackhole information paradox, in a nutshell, is the apparent difficulty in finding a unitary evolution from the initial state of the infalling matter, which forms the blackhole, to the final state of the outgoing Hawking radiation. Horowitz and Maldacena’s proposal involves a particularly clever decomposition of the Hilbert space of the stuff “inside” the horizon, and the imposition of a final state condition at the blackhole singularity.

Let $\mathcal{H}_M$ be the Hilbert space of the infalling matter, $\mathcal{H}_{\mathrm{in}}$ and $\mathcal{H}_{\mathrm{out}}$ be the Hilbert spaces of the infalling and outgoing Hawking radiation, respectively. Each of these Hilbert spaces are purported to be of dimension $N=e^S$, where $S$ is the entropy of the blackhole. We can take them to have orthonormal bases $| e_i \rangle$, $| f_i \rangle$ and $| g_i \rangle$, respectively. The Unruh state, $| \mathcal{U} \rangle \in \mathcal{H}_{\mathrm{in}}\otimes \mathcal{H}_{\mathrm{out}}$ of the Hawking radiation is

Horowitz and Maldacena propose that the final state, $\langle F | \in \mathcal{H}_M \otimes \mathcal{H}_{\mathrm{in}}$, at the singularity be given by

In that case, the evolution operator, $T: \mathcal{H}_M\to \mathcal{H}_{\mathrm{in}}$ is determined by

with the important proviso that we should consider only conditional probabilities: given that the final state at the singularity is $\langle F |$, what is the amplitude to go from some initial state in $\mathcal{H}_M$ to some final state in $\mathcal{H}_{\mathrm{out}}$? That has the effect of multiplying $\hat{T}$ by $N$, with the result that

is unitary.

But, say Gottesman and Preskill, the Hamiltonian governing the time-evolution inside the horizon is unlikely to be diagonal $H \neq H_M\otimes 1 + 1\otimes H_{\mathrm{in}}$. Instead, interactions between the infalling Hawking fluctuations and the infalling matter will produce some more general state of the stuff inside the horizon. Instead of $T$, the transition amplitude is given by

for some unitary operator $U: \mathcal{H}_M \otimes \mathcal{H}_{\mathrm{in}} \to \mathcal{H}_M \otimes \mathcal{H}_{\mathrm{in}}$.

Depending on the nature of $U$, we could have no information loss ($\tilde{T}$ unitary) or total information loss ( the final state of the Hawking radiation being totally independent of the initial state in $\mathcal{H}_M$) or anything in between.

Perhaps one can compensate for the effect of interactions by adjusting the choice of final state $\langle F |$, but it’s not exactly clear how one is supposed to do that.

The one thing that String Theory definitely doesn’t hand us is a description of quantum gravitational processes (like the formation and subsequent evaporation of a blackhole) in terms of Hilbert spaces, much less finite-dimensional ones which can be decomposed in the fashion described above. Maybe that’s a sign we need to get beyond our silly attachment to such ideas.

But I don’t know how to do that either.