Paper: Euler characteristic as a divergent sum

[Tom Leinster <tl@maths.gla.ac.uk>]

The following paper is available:

"The Euler characteristic of a category
as the sum of a divergent series"

The Euler characteristic of a cell complex is often thought of as the
alternating sum of the number of cells of each dimension.  When the
complex is infinite, the sum diverges.  Nevertheless, it can sometimes
be evaluated; in particular, this is possible when the complex is the
nerve of a finite category.  This provides an alternative definition of
the Euler characteristic of a category, which is in many cases
equivalent to the original one.

http://arxiv.org/abs/0707.0835

Many thanks to Clemens Berger for suggesting the original idea.

Best wishes,
Tom