Convergence acceleration of infinite sequences

May 31, 2009

Infinite sequences often arise in mathematics, especially in the form of the finite partial sums corresponding to an infinite series. In simple cases it possible to compute the limit (if it exists) of a sequence analytically. However, sequences for which it is very difficult or unknown how to compute the limit analytically are not uncommon in mathematics, nor in applications in science and engineering. In particular, when the sequence elements are partial sums including ever more terms from an infinite series, each sequence element becomes more time consuming to compute than the previous one. I recently came across interesting review articles (by Weniger) on techniques for accelerating the convergence of infinite sequences. Read the rest of this entry »


Future news sources

May 29, 2009

An essay how the influence of different news sources has changed over time is getting some criticism over at Pharyngula. PZ Myers mentions some problems with the claims in the essay. To be fair, though, the essay invites us to “join me on this (unscientific) tour of the last 210 years of information + 10 more years into the future” so it is isn’t claimed to be a rigorous study and much of it makes sense.

Fair or not, Blake Stacey helpfully suggests some modifications to the original graphical depiction of declining influence of different news sources, including a unit for the vertical axis.

Prisoner abuse: release photos and/or information?

May 28, 2009

The Telegraph reports that the Abu Ghraib abuse photos ‘show rape’. I’m not sure how much of it is news, but it has added new fire to the debate the Bush administration’s enhanced interrogation techniques. For instance, Hornberger at Media with Conscience asks “Was Rape an Enhanced Interrogation Technique?“. It also seems inconsistent with Obama’s statements in connection to his reversal of the decision to release more photos, more at TPM Cafe.

Considering how much outrage for instance the Mohammed caricatures caused in the muslim world, it seems to me that that Obama is right to give in to army lobbying for keeping photos classified. The release of the actual photos is in any case a distraction from the larger issue of to what extent senior officials knew about abuses and torture. The Schliesinger report (Final Report of the Independent Panel to Review DoD Detention Operations) from 2004 had this to say about Abu Ghraib and other detention facilities:

Abuses of varying severity occurred at differing locations under differing circumstances and context. They were widespread and, though inflicted on only a small percentage of those detained, they were serious both in number and effect. No approved procedures called for or allowed the kinds of abuse that in fact occurred. There is no evidence of a policy of abuse promulgated by senior officials or military authorities. Still, the abuses were not just the failure of some individuals to follow known standards, and they are more than the failure of a few leaders to enforce proper discipline. There is both institutional and personal responsibility at higher levels.

While the photos perhaps are best left classified, the information surrounding them is another matter. Let’s now lose track of larger issues like if there’s new information that gives reason to reevaluate parts of the Schliesinger report and to what extent senior officials can or should be held accountable.

Budget travel

May 27, 2009

Anyone who wants to save money by booking a very early morning flight, or just want to be prepared in case a flight is missed or long delayed, may appreciate The Guide to Sleeping in Airports. Whatever the reason may be for staying a night at an airport, this page has some tips. The main feature is the many reviews of the “night life” in airports around the world, with pointers on what to expect in the way of benches without armrests or other places to lie down, night-open caf├ęs, frequent security announcements, etc.

Hello world!

May 27, 2009

As this is the first post, it is a good place and time to say a few words about the focus of this blog. First and foremost only topics and news events that I understand well and know much about will be covered here. I’ll refrain from speculative commentary and from parroting other people’s views.

Nah. Who am I kidding? The internet has a curious ability to pull people into a mode of communication called “internet argument”, where one both feels qualified to comment on whatever topics are encountered and suffers from a craving to point out how other internet commenters are wrong. Resistance is futile. This blog will serve as an archive for my notes and comments on issues that catch my interest, as well as an invitation of feedback through comments and trackbacks. Usually, it is political news, math/science topics, and travel tips that I find notable, so a biased sampling is to be expected. That doesn’t mean that there’s a zero chance of sampling other events in metropolis, though.