lethe

is it? i got nothing by google, except for some course syllabi. wholly uninformative.

i also didn t see it anywhere in my geometry book, neither do Carmo, nor Petersen.

i would be interested to know what it is too, if anyone knows.

as far as Mike2 s description goes, it sounds a lot like the Gauss-bonnet theorem, which i know quite well. it states that the integral of the Gaussian curvature over a hyperspace gives you the euler character of the manifold, which is essentially the genus.