I know I’d implied I was off ’til Monday, but Peter Coles has written an important post that demands immediate and unqualified endorsement. Sketching two stills from his life as an openly gay man, Coles communicates the progress that has and has not been made in the way differences from the inherited social norms of sexuality are handled within academia and British society.
Archive for January, 2010
|Hubble parameter||h||0.702||H0||70.2 km/s/Mpc|
|Dark matter density||Ωch2||0.1120||Ωc||0.227|
|Baryonic matter density||Ωbh2||0.02246||Ωb||0.0455|
|Total matter density||Ωmh2||0.1344||Ωm||0.272|
|Amplitude of curvature
perturbation at k = 0.002/Mpc
|Δ2R||2.45 x 10-9|
|Spectral index of
|Size of linear density
fluctuation at 8 Mpc/h
|Redshift of matter–
|Age of the Universe||t0||13.78 Gyr|
Parameters fit directly from the data are shown in a slightly different colour; all the others have been derived from the fit parameters using the usual definitions. The determination of zeq is carried out using the WMAP 7-year data on its own. The two papers in which these figures are given are:
These papers contain many other numbers: in particular, for extensions to ΛCDM cosmology, such as neutrino species, non-zero spatial curvature and dark energy that is not the cosmological constant. I expect some of the parameters mentioned there and not here—particularly the fNLstatistics of non-Gaussianity—to gain more public attention in the next decade as observations begin to determine the properties of the cosmological inflation that occurred in the very early Universe.
A final note: I’ve written this post only because these numbers are not written on an actual webpage—they are all in pdf or postscript files. But, it also gives me a chance to congratulate the WMAP team on their ongoing achievement.
1. Riess, A. et al. (2009), ApJ 699 539, arXiv:0905.0695
2. Dark energy, or, as assumed here, the cosmological constant.
Garry Kasparov this month thinks about reviewing something-or-other in the New York Review of Books, becoming happily diverted into a discussion of what makes chess truly interesting. (I draw also from some recent conversations with S. O. Killmier.)
The big point: chess is not about who can see the most moves ahead. Computers (and humans) that win by doing this are simply winning by brute force, rather than by intelligence; in the article Kasparov memorably denigrates his result against Deep Blue as ‘losing to a $10 million alarm clock.’ If one insists that the only purpose of chess is to win, then brute force seems a very successful, though by no means infallible, way to do this. I’d like to spend a little time describing just why it isn’t fool-proof; and a lot of time showing why victory in chess is less than half the point.
Imagine you are a chess computer; in fact, imagine you are a chess computer with limitless computational power. Now here is a famous chess position—find the winning move:
I’ll let Luke post more extensively on this when time permits, but Berni, Luke & their family welcomed a new addition today, Rosalie Joy Barnes.
Congratulations to the parents!
N.b. This is a technical post, written to illustrate a question I believe to be interesting to some colleagues outside my particular discipline. I am accutely aware of its shortcomings as expository work, and pedagogical criticism is almost as welcome as an attempt to engage with the question at hand.
Well, it’s time once again* for us and you both to dance the symbiotic dance of reader feedback. We seem recently to have entered a phase where the ratio of readers to commenters on this blog is undefined, because exactly one of those numbers is zero. That’s fine; we’re here for your gratification and not the other way around.
But in addition to joining us in stirring ever more extreme compotes of popular science, unpopular mathematics and token sport and politics coverage, let’s make sure there aren’t some simple topics falling between the cracks.
Even though the irregular bursts of activity are probably a good reflection of what is possible in the post-doc blog-industrial complex, perhaps there is something to be said for working at a different place along the quality–quantity curve.
Finally, I think there is much room to include some more classical music and short-form prose fare, plus links to good recipes on one of Rachael’s blogs. I also anticipate more Micallef Tonight, Micallef P(r)ogram(me) and David McGahan clips, so don’t go on a YouTube binge right now.
* N.b. that we may not, in fact, have ever done this before.
The precursor to this post ended with the cliffhanger:
We demonstrate that when the diffraction pattern of a finite object is sampled at a sufficiently fine scale… the 3D structure of the object is in principle determined by the 2D spherical pattern.
Today, I describe how this piece of magic is achieved. (more…)
Here’s a great little contribution appearing in this week’s edition of our sister journal:
The ability to determine the structure of matter in three dimensions has profoundly advanced our understanding of nature… Here we present a 3D imaging modality, termed ankylography (derived from the Greek words ankylos meaning ‘curved’ and graphein meaning ‘writing’), which under certain circumstances enables complete 3D structure determination from a single exposure using a monochromatic incident beam.