Co-H-spaces and the Ganea conjecture

A non-simply connected co-H-space X is, up to homotopy, the total space of a fibrewise-simply connected pointed fibrewise co-Hopf fibrant j:X --> B pi (1)(X), which is a space with a co-action of B pi (1)(X) along j. We const ruct its homology decomposition, which yields a simple construction of its fibrewise localisation. Our main result is the construction of a series of co-H-spaces, each of which cannot be split into a one-point-sum of a simply connected space and a bunch of circles, thus disproving the Ganea conjectu re. (C) 2000 Elsevier Science Ltd. All rights reserved.