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Tag: wordpress

Grothendieck’s functor of points

A comment-thread well worth following while on vacation was Algebraic Geometry without Prime Ideals at the Secret Blogging Seminar. Peter Woit became lyric about it :

My nomination for the all-time highest quality discussion ever held in a blog comment section goes to the comments on this posting at Secret Blogging Seminar, where several of the best (relatively)-young algebraic geometers in the business discuss the foundations of the subject and how it should be taught.

I follow far too few comment-sections to make such a definite statement, but found the contributions by James Borger and David Ben-Zvi of exceptional high quality. They made a case for using Grothendieck’s ‘functor of points’ approach in teaching algebraic geometry instead of the ‘usual’ approach via prime spectra and their structure sheaves.

The text below was written on december 15th of last year, but never posted. As far as I recall it was meant to be part two of the ‘Brave New Geometries’-series starting with the Mumford’s treasure map post. Anyway, it may perhaps serve someone unfamiliar with Grothendieck’s functorial approach to make the first few timid steps in that directions.

Allyn Jackson’s beautiful account of Grothendieck’s life “Comme Appele du Neant, part II” (the first part of the paper can be found here) contains this gem :

“One striking characteristic of Grothendieck’s
mode of thinking is that it seemed to rely so little
on examples. This can be seen in the legend of the
so-called “Grothendieck prime”.

In a mathematical
conversation, someone suggested to Grothendieck
that they should consider a particular prime number.
“You mean an actual number?” Grothendieck
asked. The other person replied, yes, an actual
prime number. Grothendieck suggested, “All right,
take 57.”

But Grothendieck must have known that 57 is not
prime, right? Absolutely not, said David Mumford
of Brown University. “He doesn’t think concretely.””

We have seen before how Mumford’s doodles allow us to depict all ‘points’ of the affine scheme $\mathbf{spec}(\mathbb{Z}[x]) $, that is, all prime ideals of the integral polynomial ring $\mathbb{Z}[x] $.
Perhaps not too surprising, in view of the above story, Alexander Grothendieck pushed the view that one should consider all ideals, rather than just the primes. He achieved this by associating the ‘functor of points’ to an affine scheme.

Consider an arbitrary affine integral scheme $X $ with coordinate ring $\mathbb{Z}[X] = \mathbb{Z}[t_1,\ldots,t_n]/(f_1,\ldots,f_k) $, then any ringmorphism
$\phi~:~\mathbb{Z}[t_1,\ldots,t_n]/(f_1,\ldots,f_k) \rightarrow R $
is determined by an n-tuple of elements $~(r_1,\ldots,r_n) = (\phi(t_1),\ldots,\phi(t_n)) $ from $R $ which must satisfy the polynomial relations $f_i(r_1,\ldots,r_n)=0 $. Thus, Grothendieck argued, one can consider $~(r_1,\ldots,r_n) $ an an ‘$R $-point’ of $X $ and all such tuples form a set $h_X(R) $ called the set of $R $-points of $X $. But then we have a functor

$h_X~:~\mathbf{commutative rings} \rightarrow \mathbf{sets} \qquad R \mapsto h_X(R)=Rings(\mathbb{Z}[t_1,\ldots,t_n]/(f_1,\ldots,f_k),R) $

So, what is this mysterious functor in the special case of interest to us, that is when $X = \mathbf{spec}(\mathbb{Z}[x]) $?
Well, in that case there are no relations to be satisfied so any ringmorphism $\mathbb{Z}[x] \rightarrow R $ is fully determined by the image of $x $ which can be any element $r \in R $. That is, $Ring(\mathbb{Z}[x],R) = R $ and therefore Grothendieck’s functor of points
$h_{\mathbf{spec}(\mathbb{Z}[x]} $ is nothing but the forgetful functor.

But, surely the forgetful functor cannot give us interesting extra information on Mumford’s drawing?
Well, have a look at the slightly extended drawing below :



What are these ‘smudgy’ lines and ‘spiky’ points? Well, before we come to those let us consider the easier case of identifying the $R $-points in case $R $ is a domain. Then, for any $r \in R $, the inverse image of the zero prime ideal of $R $ under the ringmap $\phi_r~:~\mathbb{Z}[x] \rightarrow R $ must be a prime ideal of $\mathbb{Z}[x] $, that is, something visible in Mumford’s drawing. Let’s consider a few easy cases :

For starters, what are the $\mathbb{Z} $-points of $\mathbf{spec}(\mathbb{Z}[x]) $? Any natural number $n \in \mathbb{Z} $ determines the surjective ringmorphism $\phi_n~:~\mathbb{Z}[x] \rightarrow \mathbb{Z} $ identifying $\mathbb{Z} $ with the quotient $\mathbb{Z}[x]/(x-n) $, identifying the ‘arithmetic line’ $\mathbf{spec}(\mathbb{Z}) = { (2),(3),(5),\ldots,(p),\ldots, (0) } $ with the horizontal line in $\mathbf{spec}(\mathbb{Z}[x]) $ corresponding to the principal ideal $~(x-n) $ (such as the indicated line $~(x) $).

When $\mathbb{Q} $ are the rational numbers, then $\lambda = \frac{m}{n} $ with $m,n $ coprime integers, in which case we have $\phi_{\lambda}^{-1}(0) = (nx-m) $, hence we get again an horizontal line in $\mathbf{spec}(\mathbb{Z}[x]) $. For $ \overline{\mathbb{Q}} $, the algebraic closure of $\mathbb{Q} $ we have for any $\lambda $ that $\phi_{\lambda}^{-1}(0) = (f(x)) $ where $f(x) $ is a minimal integral polynomial for which $\lambda $ is a root.
But what happens when $K = \mathbb{C} $ and $\lambda $ is a trancendental number? Well, in that case the ringmorphism $\phi_{\lambda}~:~\mathbb{Z}[x] \rightarrow \mathbb{C} $ is injective and therefore $\phi_{\lambda}^{-1}(0) = (0) $ so we get the whole arithmetic plane!

In the case of a finite field $\mathbb{F}_{p^n} $ we have seen that there are ‘fat’ points in the arithmetic plane, corresponding to maximal ideals $~(p,f(x)) $ (with $f(x) $ a polynomial of degree $n $ which remains irreducible over $\mathbb{F}_p $), having $\mathbb{F}_{p^n} $ as their residue field. But these are not the only $\mathbb{F}_{p^n} $-points. For, take any element $\lambda \in \mathbb{F}_{p^n} $, then the map $\phi_{\lambda} $ takes $\mathbb{Z}[x] $ to the subfield of $\mathbb{F}_{p^n} $ generated by $\lambda $. That is, the $\mathbb{F}_{p^n} $-points of $\mathbf{spec}(\mathbb{Z}[x]) $ consists of all fat points with residue field $\mathbb{F}_{p^n} $, together with slightly slimmer points having as their residue field $\mathbb{F}_{p^m} $ where $m $ is a divisor of $n $. In all, there are precisely $p^n $ (that is, the number of elements of $\mathbb{F}_{p^n} $) such points, as could be expected.

Things become quickly more interesting when we consider $R $-points for rings containing nilpotent elements.

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Gina says (continued)

Via the Arcadian functor I’ve grabbed the full text of Gil Kalai’s book Gina Says: Adventures in the Blogsphere String War (part 1 and part 2) and read it on a lazy sunny afternoon.

Arguably the best paragraph is the final one, and, it might be sensible to start the book by reading it first as it clarifies Kalai’s point in collecting these comment-threads from a number of popular blogs (including not even wrong, the n-category cafe and asymptotia) :

This book is not about string theory. It is more about delicate boundaries
between greatness and megalomania, between humility and arrogance,
between fantasy and reality, between wisdom and bullshit, between
people of different stature and standing, between skepticism and
harassment, between sanity and its loss, and between truths and fallacies.
These are delicate boundaries that we witness in academics and in science
and even in blog discussions. This story offers a little salute to people’s
passion for understanding their logical and physical reality, as well as for
understanding themselves.

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introducing : the n-geometry cafe

It all started with this comment on the noncommutative geometry blog by “gabriel” :

Even though my understanding of noncommutative geometry is limited, there are some aspects that I am able to follow.
I was wondering, since there are so few blogs here, why don’t you guys forge an alliance with neverending books, you blog about noncommutative geometry anyways. That way you have another(n-category cafe) blogspot and gives well informed views(well depending on how well defined a conversational-style blog can be).

The technology to set up a ‘conversational-style blog’, where anyone can either leave twitter-like messages or more substantial posts, is available thanks to the incredible people from Automattic.

For starters, they have the sensational p2 wordpress theme : “blogging at the speed of thought”



A group blog theme for short update messages, inspired by Twitter. Featuring: Hassle-free posting from the front page. Perfect for group blogging, or as a liveblog theme. Dynamic page updates. Threaded comment display on the front page. In-line editing for posts and comments. Live tag suggestion based on previously used tags. A show/hide feature for comments, to keep things tidy. Real-time notifications when a new comment or update is posted. Super-handy keyboard shortcuts.

Next, any lively online community is open for intense debate : “supercharge your community”



Fire up the debate with commenter profiles, reputation scores, and OpenID. With IntenseDebate you’ll tap into a whole new network of sites with avid bloggers and commenters. And that’s just the tip of the iceberg!

And finally, as we want to talk math, both in posts and comments, they provide us with the WP-LaTeX plugin.

All these ingredients make up the n-geometry cafe ((with apologies to the original cafe but I simply couldn’t resist…)) to be found at noncommutative.org (explaining the ‘n’).



Anyone can walk into a Cafe and have his/her say, that’s why you’ll get automatic author-privileges if you register.

Fill in your nick and email (please take your IntenseDebate setting and consider signing up with Gravator.com to get a nice image next to your contributions), invent your own password, show that you’re human by answering the reCapcha question and you’ll get a verification email within minutes ((if you don’t get an email within the hour, please notify me)). This will take you to your admin-page, allowing you to start blogging. For more info, check out the FAQ-pages.

I’m well aware of the obvious dangers of non-moderated sites, but also a strong believer in any Cafe’s self-regulating powers…

If you are interested in noncommutative geometry, and feel like sharing, please try it out.

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Bourbakism & the queen bee syndrome

Probably the smartest move I’ve made after entering math-school was to fall in love with a feminist.

Yeah well, perhaps I’ll expand a bit on this sentence another time. For now, suffice it to say that I did pick up a few words in the process, among them : the queen bee syndrome :

women who have attained senior positions do not use their power to assist struggling young women or to change the system, thereby tacitly validating it.

A recent study by the Max Planck Institute for Human Development asserts that the QBS

likely stems from women at the top who feel threatened by other women and therefore, prefer to surround themselves with men. As a result, these Queen Bees often jeapordize the promotions of other females at their companies.

Radical feminists of the late 70-ties preferred a different ‘explanation’, clearly.

Women who fought their way to the top, they said, were convinced that overcoming all obstacles along the way made them into the strong persons they became. A variant on the ‘what doesn’t kill you, makes you stronger’-mantra, quoi. These queen bees genuinely believed it to be beneficial to the next generation of young women not to offer them any shortcuts on their journey through the glass ceiling.

But, let’s return to mathematics.

By and large, the 45+generation decides about the topics that should be (or shouldn’t be) on the current math-curriculum. They also write most of the text-books and course-notes used, and inevitably, the choices they make have an impact on the new generation of math-students.

Perhaps too little thought is given to the fact that the choices we (yes, I belong to that age group) make, the topics we deem important for new students to master, are heavily influenced by our own experiences.

In the late 60ties, early 70ties, Bourbaki-style mathematics influenced the ‘modern mathematics’ revolution in schools, certainly in Belgium through the influence of George Papy.

In kintergarten, kids learned the basics of set theory. Utensils to draw Venn diagrams were as indispensable as are pocket-calculators today. In secondary school, we had a formal axiomatic approach to geometry, we learned abstract topological spaces and other advanced topics.

Our 45+generation greatly benefitted from all of this when we started doing research. We felt comfortable with the (in retrospect, over)abstraction of the EGAs and SGAs and had little difficulties in using them or generalizing them to noncommutative levels…

Bourbakism made us into stronger mathematicians. Hence, we are convinced that new students should master it if they ever want to do ‘proper’ research.

Perhaps we pay too little attention to the fact that these new students are a lot worse prepared than we were in the old days. Every revolution inevitably provokes a counter-revolution. Secondary school mathematics sank over the last two decades to a debilitating level under the pretense of ‘usability’. Tim Gowers has an interesting Ivory tower post on this.

We may deplore this evolution, we may try to reverse it. But, until we succeed, it may not be fair to freshmen to continue stubbornly as if nothing changed since our good old days.

Perhaps, Bourbakism has become our very own queen bee syndrome…

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Now here’s an idea

Boy, do I feel stupid for having written close to 500 blog-posts hoping (in vain) they might eventually converge into a book project…

Gil Kalai is infinitely smarter. Get a fake gmail account, invent a fictitious character and start COMMENTING and provoking responses. That’s how “Gina” appeared on the scene, cut and pasted her comments (and the replies to them) and turned all of this into a book : “Gina says”, Adventures in the Blogsphere String War.

So, who’s Gina? On page 40 : “35 years of age, Gina is of Greek and Polish descent. Born in the quaint island of Crete, she currently resides in the USA, in quiet and somewhat uneventful Wichita, Kansas. Gina has a B.Sc in Mathematics (from the University of Athens, with Honors), and a Master’s Degree in Psychology (from the University of Florence, with Honors).
Currently in-between jobs (her last job was working with underprivileged children), she has a lot of free time on her hands, which gives her ample opportunities to roam the blogosphere.”

So far, the first 94 pages are there to download, the part of the book consisting of comments left at Peter Woit’s Not Even Wrong. Judging from the table of contents, Gina left further traces at the n-category cafe and Asymptotia.

Having read the first 20 odd pages in full and skimmed the rest, two remarks : (1) it shouldn’t be too difficult to borrow this idea and make a much better book out of it and (2) it raises the question about copyrights on blog-comments…

If the noncommutative geometry blog could be persuaded to awake from its present dormant state, I’d love to get some discussions started, masquerading as AG. Or, given the fact that I’ll use the summer-break to re-educate myself as an n-categorist, the guys running the cafe are hereby warned…

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math2.0-setup : final comments

Last time I promised to come back explaining how to set-up LaTeX-support, figuring I had to tell you about a few modifications I had to make in order to get Latexrender run on my mac…

A few google searches made it plain how out of touch I am on these matters (details below). But first, there was this comment to this series by Link Starbureiy :

“I took part in Gowers’ blog discussion. My input was to move things over to Google collaboration tools, like Google Knol, and perhaps Google Sites. However, those tools for large-scale collaboration may not be the best solution anymore. I like the NSN idea, but worry about it’s very long-term stability. Would you consider porting the project over to the Google App Engine so that it can be played with in the orkut sandbox (http://sandbox.orkut.com)?”

I thought I made it clear from the outset that I didn’t want to spend the rest of my life web-mastering a site such as NSN. All I wanted to show is that the technology is there free for the taking, and show that you do not have to be a wizard to get it running even on a mac…

I would really love it when some groups, or universities, on institutes, would set up something resembling this dedicated to a single arXiv-topic. Given our history, Antwerp University might be convinced to do this for math.RA but (a) I’m not going to maintain this on my own and (b) there may very well be a bandwidth problem if such a thing would become successful… (although, from past experiences and attempts I’ve made over the years, this is extremely unlikely for this target-group).

So please, if your group has some energy to spare, set-up your own math2.0-network, port it to Google Apps, Knol, Orkut or whatever, and I’d love to join and contribute to it.

As to LaTeX-support : this is trivial these days. First you need a working LaTeX-system on your virgin macbook. The best way is to download The MacTeX-2008 Distribution at work (it is a huge 1.19Gb download…). Next, install the fauxml-wordpress plugin (that is, download it to YourHome/Downloads and then drag the file faux-ml.php to the Library/WebServer/Documents/wp-content/plugins/ directory. Next, install likewise the WP-LateX plugin following the instructions, go to the configuring page and set the directory for latex and dvipng (if you follow my instructions they should be located at /usr/texbin/latex and /usr/texbin/dvipng), fill in the text color and background color you desire and clip your default latex-documentstyle/includepackages/newcommands section from your latest paper into the LaTeX Preamble window and believe me, you’re done!!!



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Ceci n’est pas un blog…

“Lieven le Bruyn’s NEVERENDINGBOOKS isn’t really a blog at all…”

Vlorbik’s unintentional [smack in the face](http://vlorbik.wordpress.com/2009/02/05/kiss-joy-as-it-flies $ left me bewildered ever since.

There aren’t that many [mathematical blogs](http://www-irma.u-strasbg.fr/article817.html) around, and, sure enough, we all have a different temperament, and hence a distinct style. I have no definition of what a mathematical blog should (or should not) be.

All I can say is that I try to reconcile an introvert character with a very public medium, partly because I think it is important for mathematics to be www-visible, but mostly because I’ve enjoyed exploring web-possibilities ever since someone told me of the existence of a language called html.

I’m a [Bauhaus](http://en.wikipedia.org/wiki/Bauhaus)-fan and hence like minimal wordpress-themes such as [Equilibrium](http://madebyon.com/equilibrium-wordpress-theme $. Perhaps this confuses some.

For this reason I’ve reinstalled the old-theme as default, and leave the reader to decide in the sidebar. This may not make this a blog yet, but it sure looks more like one…

As a one-time attempt to fit into the vast scenery of link-post-blogs, let’s try to increase the google visibility of some family-related sites (sorry, no math-links beyond) :

– The economic crisis is hitting hard at small companies such as my [sister’s-in-law](http://www.tuinkultuurlava.be) offering gardening-services.
– My god-child Tine is away for six months on a scholarship to Austria and blogging at [Tine’s adventures in Graz](http://www.tinesavontuuringraz.blogspot.com $.
– My daughter Gitte (aka here as PD1) is an [artist](http://www.gittte.be).
– My father, who will turn 79 next week, runs one of the most [popular blogs on skynet.be](http://zonnehart2008.skynetblogs.be $.

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math2.0-setup : WpMU and BuddyPress

Last time we took a clean mac os x 10.5.6 installation and upgraded it to a MySQL and Apache-PHP+ server. This hour we’ll turn it into a math2.0-test environment. That is, we will install WordPressMU (the ‘multiple user’ version of WordPress which can host 10 or 100 or thousands of blogs on your computer). Then, we’ll turn this potential into a FaceBook-like social network.

Probably it is best to test this just on your ‘localhost’ before going worldwide. Therefore, I’ll describe here the test-environment-version (the changes to make for going www I’ll describe later, but, they are minor). Here’s the first problem : WordPressMu doesn’t recognize ‘localhost’ as a valid domain, so we’ll have to use something like ‘localhost.localdomain’ and tell our server to recognize this new address.

Open TextWrangler, under File/Open File by Name type /etc/hosts and add (again you’ll be asked to unlock the file as it is owned by ‘root’ and you’ll have to provide your sudo-password when you want to save it) to the end of that file (it’s short) the line

127.0.0.1 localhost.localdomain

Save it.Your file should now look like this



You can verify this by opening Safari and pointing it to http://localhost.localdomain. You should now see the default Apache-page (no need to restart the WebServer). Next, within TextWrangler do again a File/Open File by Name and type /etc/apache2/httpd.conf and under Search/Go to Line… say 211. The highlighted line reads

AllowOverride None

change it to (again the root and sudo routine as before)

AllowOverride All

and save it. Restart the WebServer (that is, open SystemPreferences go to Sharing, unmark and remark again after a tiny delay WebSharing). Okay, I think we are set


WordPress MU :

We need a database to store everything. If your database-root password set last time is myRootPassword then do the following (change to whatever it really is). Open Terminal and type to the prompt

mysql -u root -p

and provide MyRootPassword when asked. Now we have to tell MySQL to create a database, set a database-user and password (for safety reasons it better be a new user and password, but as this is merely a test-environment…). So, to the mysql-prompt we type the following string of commands

mysql> CREATE DATABASE mywordpressMU;
Query OK, 1 row affected (0.00 sec)

mysql> GRANT ALL PRIVILEGES ON mywordpressMU.* TO root@localhost IDENTIFIED BY “MyRootPassword”;
Query OK, 0 rows affected (0.00 sec)

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.01 sec)

mysql> SET PASSWORD FOR root@localhost = OLD_PASSWORD(“MyRootPassword”);
Query OK, 0 rows affected (0.01 sec)

mysql> EXIT
Bye

The OLD_PASSWORD-command seems odd, but is needed as WordPress doesn’t like the password-structure of MySQL 5. If you forget this, you’ll get database-errors.

Open Safari and download the latest WordPressMU here. Open two Finder windows, one pointing to YourHome/Downloads (in which a new folder “wordpress-mu” is created and another one pointing to “Macintosh HD/Library/WebServer/Documents. You may as well drop the content of this Documents-directory into the Trash (the file test.php we created last time excluded).

Select everything in the first-window wordpress-mu directory and drag all of it to the second-window Documents directory.



Open Terminal and type these to the prompt

$ cd /Library/WebServer
$ sudo chmod 777 Documents
Password: (fill in your sudo password)
$ cd Documents
$ sudo chmod 777 wp-content

Point your Safari to http://localhost.localdomain/index.php and you should get a WordPress mu install page. Make sure to choose the Sub-directories option (instead of the default sub-Domain option) and fill out the required info



You should get a success-page giving you the first password to login as admin. (In case you get a database-error, remove the wp-config.php file, redo the OLD_PASSWORD command given above and repeat the install. Everything should work!). Do this, go to the Users-tab and edit your admin-account to change the password (at the bottom) to something you can remember easily.

Remember to change the directory permissions again to 755. That is, open Terminal and do

$ cd /Library/WebServer
$ sudo chmod 755 Documents
Password: (fill in your sudo password)
$ cd Documents
$ sudo chmod 755 wp-content

We now have a working WordPressMU, you can create new users and they can start new blogs, but there isn’t yet any interaction between these users and your site looks, well…



Let’s spice it up a bit with

BuddyPress :

BuddyPress is a set of WordPress MU specific plugins, each plugin adding a distinct new feature. BuddyPress contains all the features you’d expect from WordPress but aims to let members socially interact.”

We start by getting the BuddyPress Combo Download (say the .zip file) which will create a buddypress-combo directory in YourHome/Downloads. Open this directory and as before drag its entire content to /Library/WebServer/Documents/wp-content/mu-plugins.

In the buddypress-theme directory there are two subdirectories which need to be put elsewhere. The subdirectory buddypress-home must be dragged to the wp-content/themes directory (containing at the moment only the classic, default and home theme) and the subdirectory member-themes must be dragged to the wp-content directory



Log in again as admin in your WpMU via http://localhost.localdomain/wp-admin/ under Site Admin/Themes activate the BuddyPress Home Theme and press the ‘Update Themes’ button.



Similarly, in Site Admin/Options mark under ‘Allow new registrations’ the option ‘Enables. Blogs and user accounts can be created’ and update these options via the button at the bottom. Finally, under Appearance click on the BuddyPress Home Theme and activate it (top right).

Now, visit your site and change it to your liking via adding widgets. For example, add ‘Welcome’, ‘Recent Blog Posts’ and ‘Site Wide Activity’ to the left column, ‘Who’s Online’ and ‘Members’ to the center column and ‘Groups’ and ‘Meta’ to the right column.

Next, create new users (via Site Admin/Users and not via signup as this is just an offline test-version and signup sends out activating emails…), create groups, blogs and posts, let users befriend one another and send wires, etc. etc. all the things people do in a web2.0 environment.

One further comment : if you want to have avatars uploaded you’ll have to open Terminal and type the following :

$ cd /Library/WebServer/Documents
$ sudo mkdir avatars
$ sudo chown _www:admin avatars

Finally, if your iMac is a proper web-server (that is, has its own URL) you can take your math2.0-network worldwide repeating the above procedure with obvious modifications (that is, replacing localhost.localdomain by the URL of your machine). In order to get the signup/email system going you may need to install the Swift-SMTP-Mailer plugin and feed it your outgoing mail-server (also you’ll have to enable plugins in the SiteAdmin/Options).

An embryonal version of your site may then look like this one



While this may already be good enough for the rest of the world, mathematicians talk LaTeX to each other, so we’d better include LaTeX-support (and perhaps also some Wiki-support). This we will do another time…

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math2.0-setup : mysql and php+

Last time I wondered whether a set-up like WordPress.com meets FaceBook with add-ons (such as wiki- and latex-support) might be a usable environment for people working in a specific arXiv-topic.

I’ve used WordPressMU and BuddyPress to create such an embryonal environment. At first I thought I’d extend it a bit before going online but I fail to have the energy right now so I might as well make the link available. If you are into math.QA and/or math.RA you are invited to join the experiment. But, please use this site gently as I’ll have to drop it otherwise.

I’ve no desire to maintain this site indefinitely but would welcome others to set up something similar. For this reason I’ll write a couple of posts explaining how you can build it yourself when you’d have a free afternoon and a spare Mac around. Each post should not take you longer than 1 hour. Today, we’ll provide the boring but essential basics : we must get a MySQL-server and a WebServer running. Next time, I’ll take you through the WordPressMU (MU for multi-users) and BuddyPress installation. After that, we’ll add extra functionality.

We will start from a vanilla 10.5.6 installation. We will often need to edit files, so we’d better grab a good, free  texteditor : TextWrangler, drag it to Applications and place it in the Dock. We’ll also type in commands so we want the TerminalApp (to be found in Applcations/Utilities) in the Dock. SystemPreferences and Safari are already in the Dock and as we will need these tools a lot we might rearrange the Dock to look like



From left to right : the Finder, Terminal, Safari, TextWrangler and System Preferences. From now on we will mean by ‘Open …’ that you click on the ‘…’ icon. In the end we want our computer to become a web-server, so we don’t want it to go to sleep. Open SystemPreferences and look for the ‘Energy Saver’-icon, click on the ‘Show details’ button and set the ‘Put the computer to sleep when it is inactive for:’ to Never and unmark the ‘Put the hard disk(s) to sleep when possible’ at the bottom.

We will need to start or stop the WebServer so here’s how that’s done : open SystemPreferences and look for the ‘Sharing’-icon. Marking the ‘Web Sharing’ option is equivalent to starting your webserver (you can verify this by opening Safari and pointing it to http://localhost/ and you should see the default Apache-screen), unmarking it stops the webserver (check this by repeating the previous, now you should get a ‘Safari can’t connect to the server’ message).

All of this was probably trivial to you so let’s do something a bit more advanced : setting up a database-server. OSX doesn’t come with MySql, so we need to download and install it.

MySQL :

Get the latest version : choose the Mac OS X 10.5 (x86)-package and download it (they ask you to register but you can bypass this by clicking on the ‘No thanks, just take me to the downloads’-link). It is a 55.3 Mb file so this may take a couple of minutes. If all goes well this window should pop-up



Click on the mysql-5.0.67-osx10.5-x86.pkg icon and follow the instruction (defaults suffice, you’ll be asked to give your sudo password and in all it will take less than a minute). Repeat this procedure with MySQLStartupItem.pkg. Done!

To verify it, Open Terminal and type this to the prompt

sudo /Library/StartupItems/MySQLCOM/MySQLCOM start

You’ll get a scary warning message but type in your sudo-password and the Mysql-server will start. You can access it by typing

/usr/local/mysql/bin/mysql

and type exit to the mysql-prompt to leave.
In all, your interaction with the terminal should look something like this



Clearly, you do not want to type all of this every time, so we will add the mysql-location to our ‘PATH’. To do this, open TextWrangler and add this line to the blank document

export PATH=$PATH:/usr/local/mysql/bin

and save the file as .profile in your home-directory (the one with the ‘House’-icon, usually given your name). You will get a warning that .-files are reserved but go ahead anyway by clicking the use . – button). Now, open Terminal and type this

source ~./profile
echo $PATH

if all went well you should now see the mysql-location at the end of your path. From now on you’ll only have to type

mysql

to the terminal-prompt to open MySql. At the moment the root-user of your mysql has no password which isnt safe so we’d better set one. Open terminal and type

mysqladmin -u root password NEWPASSWORD

where, of course, you replace NEWPASSWORD with your choice (use only letters and numbers). From now on you can access your mysql-server by opening Terminal and typing

mysql -u root -p

and giving your password. Okay, so we’ve established our first goal, we have a working Mysql. Take a break if you need one.

better PHP

Mac 10.5 comes equipped with php5 but unfortunately it isn’t quite up to what we need. So, we need to install a better one and tell the mysql-server and the webserver to use the new one instead of the standard one.

Open Safari and grab the better php-version by going to

http://www2.entropy.ch/download/php5-5.2.5-6-beta.tar.gz

It is a 85.2 Mb file, so have a bit of patience. The file gets unzipped automatically and downloaded in the Downloads-directory. Open Finder and go there. At the moment your Downloads-directory will look like



Doubleclick on the php5-5.2.5-6-beta.tar file and a new directory will be created called php5. We will now move this directory and lay some symbolic links. Open a new Terminal window and type the following commands (and provide your sudo-password when asked)

cd Downloads
sudo mv php5 /usr/local
sudo ln -sf /usr/local/php5/entropy-php.conf /etc/apache2/other/+entropy-php.conf
sudo mkdir /var/mysql
sudo ln -s /tmp/mysql.sock /var/mysql/mysql.sock

Next, we have to tell the webserver to use this new php-version instead of the old one. This information is contained in the apache-configuration file : httpd.conf. Open TextWrangler and under ‘File’ choose the option ‘Open File by Name’. Type /etc/apache2/httpd.conf in the field that appears. The file will now appear in the main window. Under ‘Search’ choose the ‘Go to Line’ option and fill in 114 and hit the Go To button. The follwing line should now be highlighted

#LoadModule php5_module libexec/apache2/libphp5.so

immediately under it add the following line (TextWrangler will tell you that the file is owned by root and ask you whether you want to open it, click yes and make the changes)

LoadModule php5_module local/php5/libphp5.so

(observe that line 114 is commented out, that is, starts with a #, whereas your added line is not).
Save the file (Textwrangler will ask you to provide the sudo-password).

Next, we will have to tell php to communicate with the mysql-server. Again, open TextWrangler, under ‘File’ choose ‘Open File by Name’ and type in /usr/local/php5/lib/php.ini-recommended. When the file appears, under ‘Search’ choose ‘Go to Line’ and type in 810. It will read

mysql.default_socket =

Change it as follows (that is, add to it)

mysql.default_socket = /var/mysql/mysql.sock

and now choose under ‘File’ the ‘Save as…’ option. In the window change php.ini-recommended to php.ini and click Save. Done!

Testing…

Restart your webserver. Recall that this means: open SystemPreferences, choose ‘Sharing’, unmark ‘Web Server’, wait 5 seconds and then mark it again.

Open TextWranger, make a new Text document containing just one line (remove the white space between the ?-signs and the brackets) :

< ?php phpinfo() ? >

Choose ‘File’ and ‘Save as…’ and in the window that appears navigate to YourHardDisk/Library/WebServer/Documents, name the file ‘test.php’ and click the ‘Save’ button



Finally, open Safari and point it to http://localhost/test.php. Cross your fingers and if you get a screen like the one below treat yourself to something nice!



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yet another math2.0 proposal

At present, some interesting experiments are going on exploring the potential of web 2.0 for mathematical research, that is, setting up a usable math 2.0 – environment.

The starting point is that math 2.0 should be something like blogs+extras. Most mathematicians are not that interested in the latest ICT-tools, but at least they are slowly getting used to reading blogs, so we should stick to this medium and try to enhance it for online-research.

Michael Nielsen has written a couple of posts on this : an after-dinner talk about doing science online aiming at a mathematics audience, building on an essay on the future of science.

Both posts were influential to Tim Gowers‘ dream of massively collaborative mathematics. He took an interesting problem, laid down a set of 12 rules-of-conduct and invited everyone to contribute. The project is still gaining momentum and Terry Tao is also posting about it on his blog.

Michael Nielsen compared Gowers’ approach to long established practice in the open-source software community.

Another interesting experiment is nLab, a knowledge-wiki set up by the reader-community of the n-category cafe. They describe it as : “In other words: this place is like the library, or alchemist’s laboratory, in the back room of the n-Category Café. You come here to work and go there to chat.
We are hoping to create here a space for presentation and archival storage of collaborative work of encyclopedic, didactic, expositional, but also original nature. This will include, but not be limited to, the subjects being discussed every day in the n-Café.”

Both experiments are working great, aided by the authority-status of the blogger, resp. the popularity of the blog, within the research topic. But, what about topics failing to have a blogger or blog of similar status? Should we all drop our current research-interest and convert to either combinatorics or higher-categories?

History taught us in case of failing authority we’d better settle for ‘manageable anarchy’. So, here’s my math2.0-anarchy-allowed-proposal :

  • per research-topic (say, an arXiv-topic) we’ll set up a seperate online-reasearch-environment
  • anyone interested in that topic is allowed to register and fill-out a profile linking to her list of publications, describe his research interests, her ongoing projects and other trivia
  • some may want to start a blog within the environment or join an already existing one, and should be allowed to do so
  • some may opt just to read blog posts and occasionally comment, and again, should be allowed to do so
  • some may want to set up a research-group to solve a specific problem. they may choose to do this in the open, or as a covert-operation, taking on new members only by invitation
  • some may use the environment mainly for networking or chatting-up with their friends
  • some research-groups may want to start a group-blog or knowledge-wiki to archive their finds
  • surely we’ll be not discussing math in ASCII but in latex
  • anyone will be able to follow specific sub-projects via RSS-feeds
  • anyone can see site-wide activity online, see who’s currently there and chat if they feel the need
  • anyone can do whatever sensible web2.0-thing there is I forgot by age and hence by ignorance

If this seems like a tall order to satisfy, a bit of research will show that we live at the fortunate moment in time when all the basic ingredient are there, freely available, to do just that!

Over the last weeks I’ve wasted too many hours googling for help, reading-up different fora to get it all working, but … somehow succeeded. Here’s a screen-shot of my very-own NSN (for : noncommutative-social-network) :



Please allow me a few more days to tidy things up and then I’ll make the link available so that anyone interested can experiment with it.

But then, I’ve no desire to spend my days web-mastering such a site. Perhaps some of you would like to take this on, provided you’d get it on a silver plate? (that is, without having to spend too much time setting it up).

So. I’ll run a series of posts explaining how to “set-up your own math2.0 environment”. I’m not aiming at the internet-savvy ones (they’ll probably do it a lot more efficiently), but at people like myself, who are interested to investigate web-based possibilities, but need to be told where to find the very basics, such as the location of their httpd.conf file or their php.ini and such.

I’ve zeroed my MacBookPro, re-installed OSX 10.5 from scratch, upgraded it to current 10.5.6 but no extras (say, vanilla 10.5.6). And I’ll guide you from there, in all gory details, with plenty of screen-shots as I would have liked to find them when I tried to set this up.

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