Antanus Mockus

The main challenger to the incumbent party in Columbia the former mayor of Bogota, Antanas Mockus. As this profile make clear, Mockus is a man with a flair for the dramatic. According to the profile, he apparently once mooned an auditorium full of students. While mayor, he would occasionally dress up as a superhero named “Supercitizen”.

Intriguingly, the profiles list his job description as a “mathematician”, but they don’t really make clear what this means.

Martin Gardner and Hinton’s Cubes

Martin Gardner has just recently passed away. I remember really liking his books when I was in high school, but I haven’t looked at them since then.

One of his essays convinced me back in high school that trying to visualize the fourth dimension was dangerous. Charles Hinton invented a system of cubes to teach you to visualize the fourth dimension. Gardner printed a letter (copies at banubula and waggish) from someone who said that the cubes were bad for your mental health. It wasn’t until sometime after taking linear algebra that the feeling dissipated.

More on the cubes can be found at The Fairyland of Geometry.

Iry’s History of Programming Languages

I learned many new things from James Iry’s brief history of programming languages. For example, while I’ve used Lisp for some time now, I had no idea of how it all began:

John McCarthy and Paul Graham invent LISP. Due to high costs caused by a post-war depletion of the strategic parentheses reserve LISP never becomes popular. In spite of its lack of popularity, LISP (now “Lisp” or sometimes “Arc”) remains an influential language in “key algorithmic techniques such as recursion and condescension”

Condescension has never made my programs run faster, but it’s what makes writing them worthwhile.

Random Matrix Theory

I was looking for an introduction to the topic of random matrices, and I came across this survey article by Edelman and Rao on the subject. It considers a somewhat broader point of view than just results on the random distribution of eigenvalues, which are the most famous results in the subject.

One thing I found interesting is that you can explicitly calculate the Jacobian of various matrix decompositions as nonlinear functions of the matrix entries. They use this to help explain results on the random distribution of eigenvalues. More on this approach can be found in Edelman’s thesis.

How Do We Know Goldman Sachs is Guilty? Computer science

The investment bank Goldman Sachs is being sued by the SEC for allegedly selling an investment designed to lose money. The investment was built on a pool of mortgages that were likely to go into default. Initially, Erik Gerding at The Conglomerate (a legal blog) thought that the SEC would have difficulty winning the case, since Goldman had disclosed the contents of the pool. Then he had second thoughts, because of this paper, “Computational Complexity and Information Asymmetry in Financial Products”, by Arora, Barak, Brunnermeier, and Ge. The paper shows that even if you know the contents of the pool, detecting whether bad mortgages are hidden in the pool is an NP-complete problem, which is normally considered the hallmark of computational intractability.

How to Publish a Comment

In some disciplines, there is the notion of a Comment on a published article, which is what it sounds like: a short comment about the contents of the article (for example, that it’s wrong). Cat Dynamics links to an interesting account of physicist Rick Trebino’s (lengthy but ultimately successful) attempts to publish a Comment explaining why a published article is wrong.

I don’t think I’ve ever seen a Comment in a pure math journal. They’re common in statistics journals.

That Mysterious DNS

When I said that I was about to eat a big bowl of non-blogging, I didn’t mean that I was going to turn off the website, but apparently that’s what the server thought I meant. I didn’t realize initially that the site was down because I was having unrelated DNS issues, and I thought that’s why I couldn’t access the site.

I discovered that the site was back up when I received my first notification that somebody had posted spam in the comment section.