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minute changes

Published December 28, 2006 by lievenlb

These
lazy days between christmas and new-year’s eve are ideal to do finally
those things one would like to postpone indefinitely. Here is a list of
the tiny changes made to this blog : At last, an upgrade from WordPress version
2.0 to 2.0.5. Something I always defer because of the warnings to
back up databases and all changed files and preferences (and as I have
these sporadic periods of changing the PHP-code to my taste, I tend to
forget the changes I’ve made). Still, things went smoothly as far as I
can detect, the only problem I encountered was following the
instructions to the letter, such as

Special Exception:
the wp-content/cache folder should be deleted.

when what
they really mean is that one should only delete the
contents of the cache-directory. So, I had a 5-second
scare starting up the homepage and being greated with an error message
saying something to the effect that WP couldn’t write to this directory.
Apart from security reasons, this upgrade was necessary to install
some WordPress Plugins.
Top of my wish-list being RS-
Discuss.

RS Discuss is a brand new, tiny, lightweight
wordpress forum plugin that is entirely self-contained and integrates
tightly and seamlessly into your existing WordPress website. Despite its
size, it’s got everything that makes a forum a useful tool:
Full
integration with WordPress’ own user system
Multiple forum
setup
RSS feeds for forums, topics and user activity to keep
track
Search capabilities
Sidebar widget integration
Totally customisable, including different setups for different themes
Fully featured mdoerator controls including pinning and locking
topics
Clean uninstall if you don’t like it :)

So, if
you like to make your own contribution to this site (apart from
commenting), the forums (note to old schoolmates : i know it should
really be fora…) are open to all from the top menu :
forum. At present I’ve only set up a forum dedicated to discussions
on noncommutative algebra/geometry but if you like other discussions,
you will find a way to let me know. Below each post you will now
find a collection of colourful logos. They enable someone who registered
to one of the may social-bookmarking sites to add the post to their
bookmarks. Here, I used the Sociable
plugin. Last year I had a brief period experimenting with CiteULike
(see
this post ) and I intend to explore some of these bookmarking
systems further over the coming months. I’ve moved My Online Publication Page
over to this blog using the bib2html
plugin. It is now avalable from the top menu
: biblio. Every publication has its own BibTeX-popup link as well as
a link to the full PDF-file of the preprint version of the paper or book
(which may differ slightly from the published version). This page will
soon replace the older MOPP-page. I’ve moved the Archives of this
blog to the top menu :
archive using the Smart Archives
Plugin which gives a much better way to read though the past of
NeverEndingBooks. Actually getting this plugin to work did cost me some
time and (security)-worries, but these are solved, I hope. I you cannot
get it to work under WP-2.0.5, contact me and I’ll hopefully still
remember what I did. The default Calendar is replaced by an iCal-subscribable
calendar using the Event Calendar
Plugin. So far, I haven’t added upcoming events yet, but it seemed
like a good thing to have when our masterclass-noncommutative geometry
starts next semester. Note to Self : Event Calendar is incompatible with
the Sociable-plugin, so deactivate it when you want to add a new event.
And then there are some totally useless plugins which I just couldnt
resist to install. Such as the mystatus plugin
which offers an easy way to let you know what keeps me bizzy these days
(you will find it in the left-hand sidebar) or the GeoPress
plugin which enables me to add google-maps to whatever post I like.
For instance, as you may have guessed, I wrote this post from our home
and as google-maps of Antwerp have improved drasticly, you can zoom in
to my environment to any level of detail you feel appropriate…

INSERT_MAP

Added : this map seems to work with
Firefox, Flock and Camino under MacOSX but not with Safari. If you
happen to know why, please let me know.

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attention-span : one chat line

Published December 26, 2006 by lievenlb

Never
spend so much time on teaching than this semester and never felt so
depressed afterwards. The final test for the first year course on
grouptheory (60 hrs. going from nothing to Jordan-Holder and the Sylow
theorems) included the following question :

Question :
 For a subgroup $H \subset G $ define the normalizer to be the
subgroup $N_G(H) = \{ g \in G~:~gHg^{-1} = H \} $. Complete the
statement of the result for which the proof is given
below.

theorem : Let P be a Sylow subgroup of
a finite group G and suppose that H is a subgroup of G which
contains the normalizer $N_G(P) $. Then …

proof :
 Let $u \in N_G(H) $. Now, $P \subset N_G(P) \subset H $
whence $uPu^{-1} \subset uHu^{-1} = H $. Thus, $uPu^{-1} $, being of the
same order as P is also a Sylow subgroup op H. Applying the Sylow
theorems to H we infer that there exists an element $h \in H $ such
that
$h(uPu^{-1})h^{-1} = P $. This means that $hu \in N_G(P) $.
Since, by hypotheses, $N_G(P) \subset H $, it follows that $hu \in H $.
As $h \in H $ it follows that $u \in H $, finishing the proof.

A
majority of the students was unable to do this… Sure, the result was
not contained in their course-notes (if it were I\’m certain all of them
would be able to give the correct statement as well as the full proof
by heart. It makes me wonder how much they understood
of the proof of the Sylow-theorems.) They (and others) blame it on the
fact that not every triviality is spelled out in my notes or on my
\’chaotic\’ teaching-style. I fear the real reason is contained in the
post-title…

But, I\’m still lucky to be working with students
who are interested in mathematics. I assume it can get a lot worse (but
also a lot funnier)

and what about this one :

If you are (like me) in urgent need for a smile, try out
this newsvine article for more
bloopers.

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my lifestream

Published December 3, 2006 by lievenlb

The old
concept of getting your
brain subscribed to has a reincarnation into the
lifestream idea : add a page to your blog listing all
your timed actions on the web. I stumbled upon it via the
Lifestream – ala wordpress post containing a link to the original Streaming my life away
article by Jeremy Keith. After far
too much time I managed to install Chris Davis’
Lifestream wordpress plugin. Here are some comments that may make it easier to install a
lifestream page yourself. To begin, don’t download the plugin at the
top of the page, but rather scroll down to comment 886-59 by Gunnar
Hafdal and download via the link given there (or use this direct link).
This version at least contains a readme file (even after reading through
all the php-code of the other version I didn’t have a clue as how to use
it, in the readme file I finally learned that you had to create a new
page and use Lifestream as a page-template…). Next, I could’t
get it working until line 78 of stream.php was
commented out (the Copenhagen-time line). Also don’t use the
Dashboard-Manage-Lifestream page in the hope to change your
RSS-subsriptions, but rather hard-code them in the
life.php file. Bear in mind that not all RSS-data will
work with Lifestream. I’ve tried out all of the social bookmark sites of
which the logo is given at the bottom of a post, and found that only six
of them work without doing extra work : co.mments, digg,
ma.gnolia, furl, netvouz and de.lirio.us (the last one modulo the fact
that it doesnt give the accurate time). At the moment I’ve added just
co.mments, digg, magnolia and netvouz to my lifestream but I may add
other streams later. Of course one can solve problems with the other
RSS-feeds by scraping them and writing new feeds which Lifestream (or
rarther the underlying magpieRSS bundled with wordpress) can handle. I
assume this is the idea behind the other Lifestream plugin by Elliot Black (I havent
tried this one out). The last thing to do is then to change the
stream.php file so that it produces a page with more or
less the same look and feel of the rest of the blog. Apart from a few
things which I still have to remedy, I’m happy with my
Lifestream. Now it is time to have a serious go at some of these
social-bookmarking sites…

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