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May 27, 2008


Garmin Forerunner 305
Garmin Forerunner 305

My wife is the best.

For my birthday, she bought me the Dick Tracy watch pictured at left. It’s a combination stopwatch, heart rate monitor and GPS unit. Albeit a little bulky, it’s only 77g, and fits fairly comfortably on your wrist.

It records where you are (< 10 m accuracy), how fast you are going (< 0.05 m/s accuracy), and your heart rate at 5 second intervals. It gives you instant feedback about the elapsed time, your current pace, etc. It will even display a crude map showing your location, and guide you back to your starting point.

And it interfaces, via USB, with your computer. Plug it in, at the end of your run, and you get a plot like this.

Posted by distler at 10:03 AM | Permalink | Followups (2)

May 22, 2008


I don’t know about you, but I’m generally pleased with Leopard’s integration of Mail with iCal. One of the thing I find annoying, though, is the facility for adding invitations received in mail messages to your calendar. There are only two settings: “add automatically” and “off”. Why there isn’t an “ask” option is beyond me, particularly since some spammers have taken to including iCal invitations in their messages.

Previously, I’d thought that the spammers were just being maximally annoying (you have to delete their missives from two places, rather than one). But now it occurs to me that they may have more nefarious purposes in mind.

I hope the security patch, alluded to in the Advisory, appears soon.

Posted by distler at 8:59 AM | Permalink | Post a Comment

May 19, 2008

Instiki Updates

The first Release Candidate of Rails 2.1 is out. To celebrate, I updated Instiki to Rails 2.1RC1. Inscrutably, Rails reports its version number as 2.0.991. Presumably, this will change with the final release of 2.1.

Update (6/2/2008):

And it did. Instiki has been updated to run on the release version of Rails 2.1.

I’ve been looking hard at ways to speed up Instiki. There are many things which could be faster, including Ruby itself. Ruby 1.9, I’m told, is considerably faster than 1.8.6. But, for the moment, the biggest offender is one that I’m partially responsible for: the HTML5lib Sanitizer.

Posted by distler at 10:56 AM | Permalink | Followups (6)

May 12, 2008

Superconnections for Dummies

For inexplicable reasons, I got involved in a discussion with Urs Schreiber about Quillen superconnections. Urs was enamoured of the idea that Quillen superconnections might be relevant to Garrett Lisi’s “Theory of Everything.” Dubious applications, aside, Urs wanted to construct Quillen superconnections from 2\mathbb{Z}_2 graded Lie algebras, instead of Lie superalgebras. This just plain doesn’t work. So while there is, perhaps, some kind of superconnection of the sort he’s after, it’s certainly not the Quillen superconnection.

So here’s an elementary, “For Dummies,” guide to superconnections.

Posted by distler at 12:01 AM | Permalink | Followups (5)

May 11, 2008

Late Night Musings: Bug Girl Edition

The internet is a bottomless fount of the bizarre:

However heinous it is to make a living selling pubic vermin over the internet, it is somehow even more despicable to take people’s money and then NOT send them pubic lice.

Did all of this exist before the Web? Or have people just gotten a whole lot weirder in the past 15 years?

Posted by distler at 1:20 AM | Permalink | Followups (2)

May 6, 2008

Around the Blogs

Probably everyone else knew, but I was pleased to learn that Dmitry Podolsky has a new blog. Dmitry’s main focus is on cosmology (he was a student of Starobinski), but his blog runs the gamut of subjects, and he’s been churning out posts of very high quality. His latest is on the limits of validity of cosmological perturbation theory, a subject which has seen several interesting papers, since I last blogged about it.

Adam FalkowskiJester has a scathing review of a CERN seminar/recent paper by John Moffat. Moffat wants to avoid introducing a Higgs (or other new degrees of freedom) into the Standard Model, by having the theory become nonlocal at a scale of about a TeV (more precisely, at Λ W=541.189\Lambda_W=541.189 GeV (!)). Nonlocality is a sort of magic pixie dust that makes all of the obvious problems go away. The scattering amplitude for longitudinal W-bosons grows like ss, violating the unitarity bound above a TeV or so? No problem: in Moffat’s nonlocal theory, the amplitude just vanishes for s1s\gtrsim 1 TeV. This, in turn, violates the Cerulus-Martin bound1, |A(s,cosθ)|e f(θ)slog(s)|A(s,\cos\theta)| \geq e^{-f(\theta)\sqrt{s}\log(s)}? Don’t worry …

I suppose I could go on in this vein, but someone will doubtless come along and accuse me of bias. Suffice to say that introducing nonlocality in some willy-nilly fashion like this is bad mojo. And, even were it totally unfair, Jester’s account is wittier than mine.

1 The bound requires analyticity of the elastic scattering amplitude in the cut z=cosθz=\cos\theta plane and its polynomial boundedness in ss. The latter, at least for forward scattering, is intimately connected with causality. In addition to local quantum field theory, both perturbative string scattering amplitudes and various conjectured nonperturbative extensions satisfy the Cerulus-Martin bound, though, to be fair, the latter conjecture violates polynomial boundedness, which is rather suspicious.

Posted by distler at 11:01 PM | Permalink | Followups (2)

May 2, 2008

Faulty Memory

Golem has been experiencing intermittent memory problems for a little over a year, now. Originally, I ascribed the problems to cosmic rays. But their persistence seemed to belie that interpretation.

Posted by distler at 12:41 PM | Permalink | Followups (2)