Monday, August 21, 2006

Singing Vikings

They have struck again, and removing all their odes about "spam, spam, spam, lovely spam", or rather their pages upon pages of link adverts for pr0n, pi11z and war3z, took me half an hour of my maybe-generally-not-too-precious-but-still-too-precious-for-this-garbage time. I have hence reenabled comment moderation, which I disabled after no comment spam had appeared for several months in the (apparently mistaken) belief that Blogger had come up with a working spam filter. Please accept my apologies for any inconvenience this measure may cause.

On the physics front, everything is now abuzz with news that the Chandra X-ray observatory has made the most direct observation of dark matter so far. Read more about it from Rob Knop, Steinn SigurĂ°sson, Chad Orzel, Clifford Johnson and Sean Carroll, or read the original NASA press release. The BBC is also reporting.

Thursday, August 17, 2006

More links

This is just another collection of links and such.

There is a new group blog in town: over at Jacques Distler's golem, arch-proto-blogger John Baez, String Coffe Table-host Urs Schreiber and philosopher of mathematics David Corfield have formed the n-Category Café, where they will discuss the mathematical, physical and philosophical impact and applications of n-Categories.

Also new to our blogroll are Cosmic Variance contributor Clifford Johnson's new personal blog Asymtotia, and the apparently anonymous Superweak.

The BBC has a number of astronomy stories among the news: Here they discuss the new definition of a planet, which for some reason really captivates the general public, and here they report on a recent observation by the Hubble telescope of the dimmest stars in the Milky Way, while here they report about a recent determination of the Milky Way's age using the VLT telescope array. No particle physics new there, unfortunately.

For many parallel talks given at the Lattice 2006 conference, slides are now also available (just follow the links that used to lead to the abstracts). In case anybody is interested (or bored) enough to care, here are mine. The first proceedings contributions should start appearing on the arXiv in the next couple of weeks or so, once the participants have received the necessary LaTeX files and instructions from Proceedings of Science.

Thursday, August 10, 2006

News summary

No, this is not about the threat to air travel (although that is something currently on my mind, as I am going to fly to Europe at the end of this month, and a couple of days in the UK were actually part of the plan); this is a physics blog, and I will leave publicly debating the current political events to people with greater expertise (and it appears I'm not alone in doing so). This post is about some science news that may have been buried among all the terror and war.

James Van Allen, a pioneer of space exploration and the discoverer of the radiation belts named after him, died yesterday. The NYT article mentions his participation in "Project Argus, the firing of three atomic bombs 300 miles aloft over the South Atlantic." I had never heard of this before, and I think it bears repeating that in spite of the threat of terrorism, the world is probably a safer place overall today than it was at the height of the Cold War, when the impending total annihilation of all life on Earth by all-out global thermonuclear warfare was a distinct possibility (I recently happened to switch on my TV when War Games was being shown, and I remember thinking "well, at least nuclear war is a very remote threat today").

The Perseids meteor shower peaks this Saturday, but the still almost full moon will probably make for less than ideal viewing conditions; still, any hobby astronomers and star-lovers out there should probably spend Saturday evening outdoors with their eyes on the sky.

Via Tommaso Dorigo, Superweak has an interesting post on Dalitz plots. Richard Dalitz, who died in January of this year, was the Ph.D. supervisor of my own Ph.D. supervisor, Ron Horgan; the world is small.

Wednesday, August 09, 2006

Lattice 2006 -- Summary

As threatened earlier, here is my personal review of the Lattice 2006 conference, in the form of an incomplete list of disjointed observations:

Driven by the RHIC data, QCD at finite temperature and/or chemical potential is rapidly becoming a leading subfield within lattice QCD; at this meeting, seven out of 22 plenary talks were about some aspect of QCD thermodynamics, and the number of parallel talks on "High temperature and density" topics was second only to that of the traditionally most numerous spectroscopy talks.

The debate about the validity of the fourth-root prescription for staggered fermions, which an anonymous observer called "the staggered wars", shows no sign of coming to an end. Although a lot of progress has been made recently towards showing the correctness of the rooting prescription, a number of unattractive features have been found at the same time, fueling the flames.

Progress regarding more accurate determinations of CKM matrix elements from lattice QCD is slow, but steady; a lot of this work is very difficult, since getting high precision requires good control over perturbative errors and chiral extrapolations, and both lattice perturbation theory and chiral perturbation theory are hard and suffer from a lack of practitioners.

The AdS/CFT correspondence is beginning to become a topic of interest to researchers working on QCD, and string theory returns to its origins in the strong interactions where it may become a helpful tool to build and solve models of QCD.

Dynamical simulations with overlap fermions are arriving, but it will be a while until they get to the range of lattice spacings, lattice sizes and quark masses that have been studied using staggered fermions.

Everyone will be able to form their own opinion on what was new, what was hot and what was not, once the proceeedings have been published by Proceedings of Science (and before that, when there will be a flood of new papers on the currently fairly quiet hep-lat arXiv).