Published online by Cambridge University Press: 24 October 2008
Recall that a categorical covering of a space B is a covering by closed sets each of which is contractible in B. Suppose that B admits a finite categorical covering, and hence one where the number of sets is minimal. The category of B is then defined to be one less than that minimum number. Category is generally associated with nilpotency, in homotopy theory. In this note we describe a further illustration of this, from the theory of fibre spaces.