Friday, 18 July 2008

Erdös Numbers: The Kevin Bacon Game for Mathematicians

I first heard about Erdös Numbers a few years ago when it cropped up in a quiz I was doing. Basically an Erdös number signifies your closeness (based on academic collaboration) to the now deceased Hungarian mathematician Paul Erdös. Erdös himself has an Erdös number of 0 while those who have published work with him have an Erdös number of 1 and their co-authors have a Erdös number of 2 etc. It is very like the more well known (in popular culture at least) Kevin Bacon game which I'm sure you have all played at one time or another. Anyway having solved the quiz question all those years ago I thought no more about Erdös numbers.... until today.

It turns out that I have an Erdös number of 4. The head of the research group I work in, Yorick Wilks, realised from an old publication list that he actually has an Erdös number of 2 due to a paper he published with Frank Harary who published two papers with Erdös and hence has an Erdös number of 1. Now I haven't published any papers with Yorick but my PhD supervisor has and so my Erdös number is 4.

Here are details of the four papers showing the link from me all the way back to Erdös
  • Mark A. Greenwood and Robert Gaizauskas. Using a Named Entity Tagger to Generalise Surface Matching Text Patterns for Question Answering. In Proceedings of the Workshop on Natural Language Processing for Question Answering (EACL03), pages 29-34, Budapest, Hungary, April 14, 2003.

  • Robert Gaizauskas and Yorick Wilks. Information Extraction: Beyond Document Retrieval. Journal of Documentation 54(1), 70-105, 1998

  • Frank Harary and Yorick Wilks. On Unidirectional Linguistic Comprehension. New Mexico State University, MCCS-92-238.

  • Paul Erdös, Frank Harary and W.T. Tutte. On the dimension of a graph. Mathematika, 12 (1965)
The Erdös Number Project (which tracks all Erdös number related info) states that the average finite Erdös number is 4.65, which means mine is slightly lower than average. Also it appears I have the same Erdös number as Bill Gates -- not sure if that is a good thing or not!

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