Archiv der Mathematik

, 96:321

On the rank of compact p-adic Lie groups


DOI: 10.1007/s00013-011-0240-7

Cite this article as:
Klopsch, B. Arch. Math. (2011) 96: 321. doi:10.1007/s00013-011-0240-7


The rank of a profinite group G is the basic invariant \({{\rm rk}(G):={\rm sup}\{d(H) \mid H \leq G\}}\), where H ranges over all closed subgroups of G and d(H) denotes the minimal cardinality of a topological generating set for H. A compact topological group G admits the structure of a p-adic Lie group if and only if it contains an open pro-p subgroup of finite rank. For every compact p-adic Lie group G one has rk(G) ≥ dim(G), where dim(G) denotes the dimension of G as a p-adic manifold. In this paper we consider the converse problem, bounding rk(G) in terms of dim(G). Every profinite group G of finite rank admits a maximal finite normal subgroup, its periodic radical π(G). One of our main results is the following. Let G be a compact p-adic Lie group such that π(G) = 1, and suppose that p is odd. If \(\{g \in G \mid g^{p-1}=1 \}\) is equal to {1}, then rk(G) = dim(G).

Mathematics Subject Classification (2000)

Primary 20E18 Secondary 22E20 


Compact p-adic Lie group Rank Dimension Number of generators 

Copyright information

© Springer Basel AG 2011

Authors and Affiliations

  1. 1.Department of MathematicsRoyal Holloway, University of LondonEghamUK