# Hinges fail

About two years ago I bought a MacBook Air. I was worried about the lack of an optical disk reader, about the inaccessible battery and the presence of only one USB connection, but in the past two years I don’t remember ever needing the disk reader on the road (I have an external one at home), only a few times I wished for an extra USB port, and the battery has been holding up all right.

I have, however, encountered some completely unexpected problems. One is that the machine overheats very quickly if it does a computation-intensive task, and it has the “feature” that, if the temperature gets high, it shuts down one of the cores and makes the other go at about 40% speed. This means that it is not possible to connect it to a tv to watch movies from netflix or tv shows from hulu, because within half an hour it reaches the temperature that triggers the slowdown, at which point it skips so many frames that the movie looks like a slide show.

I also wish I could add more RAM. (The memory chips are soldered on the motherboard.)

Then last week I heard a cracking noise when opening it, and the screen would fall back instead of holding its position.

Despite the seemingly sturdy metal construction, the hinges had cracked:

Well, not a big deal, I thought, how expensive can replacement hinges be? Very expensive, a google search revealed.

The design of the computer is such that to repair the hinges they need to replace the screen. Not just the metal shell that covers the screen, but the LCD screen itself too, for a cost in the ballpark of \$800.

“Thankfully,” Apple will repair it for free even if my warranty has long expired.

The announcement of the free repair offer tells a story all by itself. First, that there should be an official policy for this problem shows how many people had this problem and how defective was the original design. (A google search also shows that.) Notice the compound design failures of having a break that (1) is so expensive to fix and (2) is so likely to occur. Second, the announcement offers a refund to those who paid for the repair in the past: indeed for a while people were having this break while their warranty was active and Apple would make them pay for the repair, claiming that the users were responsible for breaking the hinges, evidently because they used the computer in a way that it was not designed for, such by opening and closing it on occasion.

# Presenting a Beamer Talk the Right Way

I sometimes use Beamer (a LaTex package) to prepare slides for conference or seminar presentations, and sometimes I use Keynote.

Keynote has a simple but very desirable feature: during the presentation, the laptop screen, instead of going blank or showing a copy of the current slide, shows the current slide, and the next slide, and a timer. If you have ever used Keynote, you know how useful it is to have the time and the next slide always in front of you.

When a slide presentation is prepared with Beamer, the output is a pdf file which is then displayed using Acrobat Reader, or the OS X Preview application, and one gets a blank screen on the laptop during the presentation. Since pdf handling is built natively into OS X, and since a timer and a next-slide display are really simple things, I assumed there would be some program that would do a Keynote-style presentation from a pdf file.

Unfortunately, I wasn’t able to find any such thing for OS X. (Interestingly, there is a program for Windows that does that.)

Thankfully, Melissa O’Neil has done the next best thing, or maybe an equally good thing: a program that converts a pdf file into a Keynote file. So you can create your pdf with Beamer, then convert it to the Keynote format, and use Keynote to display the presentation.

Not the cleanest of workflows, but it works. Thanks, Melissa O’Neil!

# Collaborative Filtering and Partitioning

To decide the scheduling of the coming FOCS, and of any conference with parallel sessions, it would be great to have the following tool: a site where prospective participants can browse the list of accepted papers and their abstracts, decide which talks sound interesting, and select them in a checklist. After a while, based on the lists and some simple algorithm (probably, spectral techniques would work), a program automatically selects a schedule with few conflicts and with similar papers in the same session.

Optionally, after the schedule is finalized and the submission of lists is closed, the site could send a “you might also be interested in…” list to the registered users who sent in their lists, as a “reward.”

Does something like this exist? If not, would any reader(s) want to take it on as a volunteer project? It would have to be done within the next two weeks or so, but I believe that for someone who knows how to use the right tools it is a matter of a couple of days of coding. I can host the site at Stanford.

# Mathematical Research and New Collaboration Tools

Next Tuesday, May 18, at noon California time, I will speak (in Italian) in a free `webcast’ organized by Oilproject on the impact of new collaboration and communication tools in mathematical research. (A recording will be available after the event.)

Those who watch it live can ask questions, and I haven’t planned very specifically what I will talk about, hoping that the questions will drive the discussion. Two things that I want to talk about are:

• the story of Polymath’s combinatorial proof of the Density Hales–Jewett theorem, demonstrating the viability of a “massively collaborative” approach to mathematical research, and what it means for mathematics, both “philosophically” and practically.
• the way mathematical blogs have become an effective way to disseminate the kind of mathematical lore (the insights, the concrete ways of visualizing very abstract constructions, the facts that are “well known” to experts and “implicit” in classic papers, but impossible to see for the non-experts, etc.) that cannot be found in monographs and research articles, and that, previously, was exclusively handed out from advisors to advisees and from colleague to colleague. This will make it much easier for the brilliant students who don’t happen to be in the top schools to master their research area and make new breakthroughs.

This will be part of a series of webcasts on how new communication technologies affect the economy, news, technologies, science, etc., with some notable speakers. Last week Stefano Andreoli spoke about spinoza.it, which is roughly The Onion of Italy.

# The Mystery Lamp

I have to buy a lamp for my office desk, and I was planning to either buy the Tizio lamp, which I have at home and that I think is the most beautiful desk lamp in production, or the Tolomeo, which works better in terms of actually illuminating, and is almost as good-looking.

Searching online, I found out that, apparently, since 2006 Artemide has been making an LED version of the Tolomeo

which looks amazing. I have, however, never seen it in a store, I haven’t been able to find any review on the web other than the marketing information from Artemide, and, while it can be ordered online, it seems that no store in San Francisco has it in store to check it out.

Usually, the light of LEDs is cold and unpleasant, so I wouldn’t buy it sight unseen. (Plus, it’s supposed to be quite small, so I am afraid it could be too small for a large desk.) So I turn to the powers of the internet: have you, or maybe your roommate’s sister in law’s cousin, seen it in real life?

If not, has any of you used an LED lamp as a desk light? How did it work out for you?

# LaTeX2WP minor update

LaTeX2WP is a program that converts a LaTeX file into something that is ready to be cut and pasted into the WordPress online editor. It makes it easier to write mathematical posts, to post lecture notes on WordPress, and so on.

A new version is now available, which fixes a couple of bugs:

• WordPress has trouble if a mathematical expression containing $<$ is followed by a mathematical expression containing $>$. This is prevented by converting the inequality symbols to their HTML “character codes.”
• The previous version of LaTeX2WP had trouble with long sentences in square brackets; this is fixed.

In addition, \S for § and \v{C} for Č (as “in Stone–Čech compactification”) now work.

# LaTeX2WP Update

I have posted a new version of LaTeX2WP, a program that converts a LaTeX file into a format that is ready to be copied into WordPress.

The new version fixes some bugs and has some new features:

• Thanks to code contributed by Radu Grigore, it is now possible to nest bold inside italic, and there is a better overall support for font styles. (Which is also easier to customize.)
• `eqnarray*` is now supported.
• LaTeX commands are correctly “tokenized” before certain macros are applied. For example, LaTeX2WP recognizes the macro \P for \mathop{\mathbb P}. In the previous version, however, the above transformation would also be applied to the initial \P in \Phi. Thanks to Terry Tao and “ccarminat” for noticing this bug.
• Commands such as \\$ and \% now work in math mode. (\& does not work, but this seems to be a WordPress problem.) Thanks to Atri Rudra for noticing this bug.
• Quotation marks are applied to the URL in \href and \hrefnospan. The lack of such quotation marks sometimes creates problems with \hrefnosnap.

# Converting LaTeX to WordPress

Last month, I have written a program that converts a LaTeX document into a format that is ready to be copied and pasted into the WordPress editor.

I have been using it to post the notes of my cryptography class here, as well as some other posts.

Terry Tao has tested it on a couple of posts. Thanks to his feedback, the current version, while surely bug-filled and very limited, is stable enough to be used by other people. It is now available to anybody who might be interested.

What is the point of this program?