
As far as I know (but I am fairly ignorant) the arXiv does not provide RSS feeds for a particular section, say mathRA. Still it would be a good idea for anyone having a news aggregator to follows some weblogs and newschannels having RSS syndication. So I decided to write one as my first Perlexercise… Read more »

I just finished the formal lecturepart of the course Projects in noncommutative geometry (btw. I am completely exhausted after this afternoon\’s session but hopeful that some students actually may do something with my crazy ideas), springtime seems to have arrived and next week the eastervacation starts so it may be time to have some fun… Read more »

Yesterday morning I thought that I could use some discussions I had a week before with Markus Reineke to begin to make sense of one sentence in Kontsevich’ Arbeitstagung talk Noncommutative smooth spaces : It seems plausible that Borcherds’ infinite rank algebras with Monstrous symmetry can be realized inside HallRingel algebras for some small smooth… Read more »

If I ever get our home automation system configured I’ll use my (partly broken) old iBook as my Indigoserver (or my MisterHouseserver when I brush up my Perlknowledge). It should then run quietly put away somewhere and I don’t want to take it out every time I want to add another routine to the program…. Read more »

Tomorrow I’ll start with the course Projects in noncommutative geometry in our masterclass. The idea of this course (and its companion Projects in noncommutative algebra run by Fred Van Oystaeyen) is that students should make a small (original if possible) work, that may eventually lead to a publication. At this moment the students have seen… Read more »

I bought a couple of X10building blocks : a tranceiver, an appliance and a lampmodule, a computerinterface and a motion detector and started playing using the Indigo helppage. All modules worked immediately and getting them under Indigo‘s control was also no problem. Clearly it is fun to control a living room lamp and the coffee… Read more »

I\’ve barely managed to implement the six great tips for homemade dot mac servers by Alan Graham or he is already off on a new project : Home Automation with Mac OS X. I thought that home automation only could be installed in new, highly wired, houses but I was wrong. In part 1 Alan… Read more »

I haven’t mastered by far all nuances of this fine device yet, but here it is : a first approximation to my geek code —–BEGIN GEEK CODE BLOCK—– Version: 3.1 GM d s: a+ C+ UB+ P+ L+ E W++ N o? K w– O? M+ V? PS+ PE Y+ PGP t 5? X R… Read more »

To a large extent mathematics has to do with elaborate typography. Many youngsters have been attracted over the centuries to maths because they wanted to understand the meaning of these beautiful pages filled with integrals, partial derivatives and other bizarre hieroglyphs. But now we have come to the point that this obsession for symbols is… Read more »

Carbon Copy Cloner is a tool to make a full backup of your harddisk on an external firewire disk or iPod. Here’s how it sells itself Have you ever wanted a simple, complete, bootable backup of your hard drive? Have you ever wanted to upgrade to a larger hard drive with minimal hassle and without… Read more »

Over the last couple of days I’ve been experimenting a bit with different backup methods. To begin, I did try out ExecutiveSync and its successor You Syncronize but they are very, very slow. Not only did the first synchronizing of a 0.5 Gb Folder between two computers over our Airportnetwork took over 2.5 hrs, but… Read more »

Again I spend the whole morning preparing my talks for tomorrow in the master class. Here is an outline of what I will cover : – examples of noncommutative points and curves. Grothendieck’s characterization of commutative regular algebras by the lifting property and a proof that this lifting property in the category alg of all… Read more »

Tweedledum is a firstgeneration iMac (233 MHz slotloading, 192Mb RAM, No Airport) whereas Tweedledee is 2ndgeneration (350 MHz frontloading, 192Mb RAM, Airport card). A couple of weeks ago I replaced their original harddiscs (4 Gb resp. 6 Gb) by fat 120 Gb discs and from this weekend they serve as our backupfacility. Tweedledee is connected… Read more »

Today I did prepare my lectures for tomorrow for the NOG masterclass on noncommutative geometry. I\’m still doubting whether it is worth TeXing my handwritten notes. Anyway, here is what I will cover tomorrow : – Examples of lalgebras (btw. l is an arbitrary field) : matrixalgebras, groupalgebras lG of finite groups, polynomial algebras, free… Read more »

This week I reread with pleasure all 918 pages of Cryptonomicon by Neal Stephenson and found out that last time I had been extremely choosy in subplots. There are 4 major plots : one contemporary (a couple of geeks trying to set up a datahaven) and three WW2 stories : the Waterhouseplot about cracking Enigma… Read more »

We have seen that a noncommutative $l$point is an algebra$P=S_1 \\oplus … \\oplus S_k$with each $S_i$ a simple finite dimensional $l$algebra with center $L_i$ which is a separable extension of $l$. The centers of these noncommutative points (that is the algebras $L_1 \\oplus … \\oplus L_k$) are the open sets of a Grothendiecktopology on $l$…. Read more »

The game of Fox and Geese is usually played on a crosslike board. I learned about it from the second volume of the first edition of Winning Ways for your Mathematical Plays which is now reprinted as number 3 of the series. In the first edition, Elwyn Berlekamp, John Conway and Richard Guy claimed that… Read more »

The game of SNORT was invented by Simon Norton. The rules of its SNORTgoversion are : black and white take turns in putting a stone on a goboard such that no two stones of different colour occupy neighbouring spots. In contrast to COLgo it is a hot game meaning that many of its positions are… Read more »

Last time we have seen that in order to classify all noncommutative $l$points one needs to control the finite dimensional simple algebras having as their center a finite dimensional fieldextension of $l$. We have seen that the equivalence classes of simple algebras with the same center $L$ form an Abelian group, the Brauer group. The… Read more »

More than a month ago I started a long term project trying to make the best of our little home network. The first couple of weeks I managed to get iTunes, iPhoto and iMoviefiles flowing from any computer to the living room (the TVset for photo and mpegfiles and squeezebox for audio files). The last… Read more »

Never thought that I would ever consider Galois descent of semigroup coalgebras but in preparing for my talks for the masterclass it came about naturally. Let A be a formally smooth algebra (sometimes called a quasifree algebra, I prefer the terminology noncommutative curve) over an arbitrary basefield k. What, if anything, can be said about… Read more »

Noncommutative geometry seems pretty trivial compared to commutative geometry : there are just two types of manifolds, points and curves. However, nobody knows how to start classifying these noncommutative curves. I do have a conjecture that any noncommutative curve can (up to noncommutative birationality) be constructed from hereditary orders over commutative curves by universal methods… Read more »

For someone as clumsy as me, it is no real surprise to loose one in three hard disks, but what happened yesterday was a bit puzzling at first. I tried to replace the original 4 Gb hard disk of an original iMac (a tray loading iMac) following the instructions of the MacWorld : how to… Read more »

The GAPpackage is very good in working with finite fields or Abelian extensions of the Rational numbers, but sooner or later we will need to use the coordinate ring or function field of an affine variety for which it is hopeless. On the other hand, there is an excellent free package to do these calculations… Read more »

GAP the Groups, Algorithms, and Programmingtool (developed by two groups, one in St. Andrews, the other in Aachen) is the package if you want to work with (finite or finitely presented) groups, but it has also some routines for algebras, fields, division algebras, Lie algebras and the like. For years now it is available on… Read more »
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