Paul Erdös (1913-1996) holds the record for the most academic publications in mathematics. He was also famously itinerant, traveling continuously between the homes of colleagues all over the world. It is said that upon arrival he would announce, “My brain is open.” A few days later, after collaborating on some papers, he would move on. Despite (or because of) his eccentricities, Erdös was a beloved figure in mathematics and is still remembered fondly by many whose lives he touched. (A very nice segment of the Radiolab episode Numbers discusses Erdös.)
One way in which Erdös’ collaborative relationships and their influence is memorialized is through Erdös numbers. The concept is similar to the more popularly known Bacon numbers (as in six degrees of Kevin Bacon). Erdös himself has Erdös number zero. Individuals who coauthored a paper with him have Erdös number one. Individuals who are coauthors of his coauthors have Erdös number two, and so on.
My Erdös number is four, which I obtained by sending an e-mail to Jerry Grossman who runs the Erdös Number Project. Here’s my publication path to Erdös:
- Erdös P, Hartman S. On sequences of distances of a sequence. Colloq. Math. 17:191-193. 1976.
- Hartman S, Meyer Y. Interpolation harmonique sur les copacts. Colloq. Math. 40(2):265-276. 1978/79.
- Daoudi K, Levy J, Meyer Y. Construction of continuous functions with prescribed local regularity. Constr. Approx 14(3):349-385. 1998.
- Daoudi K, Frakt A, Willsky A. Multiscale autoregressive models and wavelets. IEEE Trans. Inform. Theory 45(3):828-845. 1999.
The implication is that anyone with whom I’ve published has an Erdös number no larger than five. Does that apply to those with whom I’ve co-authored a blog post? Not officially, but let’s just give them Blogös numbers of five for fun (Ian, Steve, Julian, that means you).