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Tag: geometry

a good day at the arxiv

The
arXiv is a bit like cable tv : on certain days there seems to be nothing
interesting on, whereas on others it’s hard to decide what to see in
real time and what to record for later. Today was one of the better
days, at least on the arXiv. Pavel Etingof submitted the
notes of a course he gave at ETH in the spring and summer of 2005 Lectures on
Calogero-Moser systems
. I always sympathize with people taking time
to explain what they are interested in to non-experts, especially if
they even take more time to write up course notes so that the rest of us
can also benefit from these talks. Besides, it is always more rewarding
to learn a topic from a key-figure such as Etingof, rather than sitting
through talks on this given by people who only embrace a topic as a
career move. However, as I’m no longer that much into Calogero-Moser
stuff I’ve put Pavel’s notes in recording mode as I definitely have to
spend some time getting through that other paper posted today : Notes on A-infinity
algebras, A-infinity categories and non-commutative geometry. I
by
Maxim
Kontsevich
and Yan
Soibelman
. They really come close to things that interest me right
now and although I’m not the greatest coalgebra-fan, they may give me
just enough reasons to bite the bullet. On a different topic : with
plenty of help from Jacques Distler, my
neverending planet
is now also serving MathML, but you need to view it using Firefox and
have all the required fonts
installed.

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writing with gloves on

Okay, let’s have it out in the open :

I’m officially diagnosed as being depressed by both PD1 and PD2!

Coming from the two top experience-experts on my mood swings, I’d better take this
seriously. So, do they come up with an explanation for this ‘depression’?

PD1 blames it on the celebrated mid-life-crisis which in her world is merely the generic phrase uttered when a parent does something ‘odd’.

If thePartner wants to spend some time among old friends, or wants to get involved in community work, it’s called ‘mid-life crisis’.

When both of us join a demonstration for the first time in over a decade, it’s MLC etc. etc.

In recent years I heard her say the MLC- phrase often enough referring to her friends’ parents and thePartner but somehow I always got away, until recently…

PD2 blames it on my turning 48 last week, a fact I cannot deny but then, what’s so special about 48? I don’t get it.

Feeble as their explanations may be, they still may have a point. Sure, some losses do affect me. Some recent, some imminent, some unfortunately permanent, some hopefully temporary…

I realise this is a bit cryptic to the uninitiated, but then I’ve given up writing about personal stuff a long time ago (to the dismay of PD2 who would welcome more web-presence when self-googling…).

But wait… Hey, that may be part of the problem :

I’ve given up writing about so many things recently that there’s hardly anything sufficiently interesting left to write about.

In the post-Dutroux scare I did remove all pictures and references to our daughters from my web-pages, for you don’t want to know the weirdos that have a look at it and you definitely do not want to think about what they might do when they obtain my address from the university web-page….

Surely a valid point. So, away with all writing about personal stuff.

Then, more recently (and I hope at least some of you noticed it…) I’ve imposed a ban on critical postings about people or events going on in noncommutative algebra/geometry. The reason behind this decision is personal, so if I didnt tell you in private you’ll never find it here.

Speaking about this with Paul Smith at the last Oberwolfach, he had an hilarious reply.

“I wouldn’t say you were critical. I’d say you are sometimes pretty intense and I love it, as long as I’m not on the receiving end…”

But see, that’s just the problem. Mathematicians are so vane that there is always someone who feels to be on the receiving end!

Let’s say, hypothetically speaking, that I write a somewhat critical post about the ongoing cluster-algebra hype, we all know some people who will not like it. Ditto about (again hypothetically…) symplectic-reflection algebras, ditto about etc. etc.

Compare this with the entertaining about-life-or-death fights going on in physics-blogs. If you don’t know what I’m talking about and want to have a good laugh, have a go at the comments to this Not Even Wrong Post.

Possibly, I should come to terms with the fact that blogging is an activity which will never be tolerated by the autism-enriched environment of mathematicians and that I should just give it up.

Or, perhaps, I should regain my writing-freedom and blog about whatever I feel strongly about at that particular moment in time (and remember, I do suffer from violent mood-swings so these opinions may change overnight…), be it critical or if you want ‘intense’, and hope that not too many will think they are on the receiving end…

I realize that I will sometimes be accused of ‘jealousy’, sometimes of being ‘frustrated’. But, let’s face it : bottling up one’s frustrations, that’s precisely the thing that leads to a genuine depression…

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sage

SAGE
(which stands for ‘Software for Algebra and Geometry
Experimentation’) includes and offers an interface to GAP, Singular,
Maxima and even PARI as
well as an interface to other packages such as Maple, Magma and
Mathematica (see here
for a full list of its features). More importantly, Sage offers a binary
for both PPC and Intel-Macs! I did check this out and it runs without
problems, in fact, after this initial check I installed from the sources
on my MacBook Pro and after one hour of compiling I did have working
(though not full) versions of GAP, Maxima and Singular. At first I
was a bit worried that only small subsets of the three systems were
installed, but it is quite easy to extend your Sage with additional
packages. From the Unix-prompt do a sage -optional
and you will get a list of all (additional) packages you have already
installed and those available for installation. SAGE is pretty well
documented with tutorials and reference manual to be found here. Even if you do not want to learn (yet) the Sage-commands but just
want to continue using the programs under its hood, this is pretty easy.
For example, to get to Maxima, you only have to type
!maxima from the sage-prompt to open up a maxima-session
(and similarly for Gap and Singular).

Bill
Schelter’s Affine-package is not included, but you can load and install
it from the maxima-prompt by load("affine.lisp"); but some
commands such as ‘fast_central_elements’ do not seem to
work as expected (or maybe I forgot the drill over the years, I’ll try
it out again).

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