Bulletin of the London Mathematical Society Advance Access originally published online on October 3, 2008
Bulletin of the London Mathematical Society 2008 40(6):1065-1069; doi:10.1112/blms/bdn089
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© 2008 London Mathematical Society
Pro-p groups of positive deficiency
School of Mathematics and Statistics
University of Sydney
Sydney, NSW 2006
Australia
jonh@maths.usyd.edu.au
NWF-I Mathematik
Universität Regensburg
D-93040 Regensburg
Germany
Received 28 February 2008. Revision received 9 July 2008.
Let
be a finitely presentable pro-p group with a nontrivial, finitely generated closed normal subgroup N of infinite index. Then def (
)
1, and if def (
) = 1 then
is a pro-p duality group of dimension 2, N is a free pro-p group and
/N is virtually free. In particular, if the centre of
is nontrivial and def (
)
1, then def (
) = 1, cd G
2 and
is virtually a direct product F x
p, with F a finitely generated free pro-p group.
2000 Mathematics Subject Classification 20E18.