Geodesic
Fixed Points of Automorphisms of Free Pro-p Groups of Rank 2
Canadian journal of mathematics, Tome 47 (1995) no. 2, pp. 383-404

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Let p be a prime number, and let F be a free pro-p group of rank two. Consider an automorphism α of F of finite order m, and let FixF (α) = {x ∈ F | α(x) = x} be the subgroup of F consisting of the elements fixed by α. It is known that if m is prime to p and α = idF, then the rank of FixF(α) is infinite. In this paper we show that if m is a finite power pr of p, the rank of FixF(α) is at most 2. We conjecture that if the rank of F is n and the order of a is a power of α, then rank (FixF (α)) ≤ n.
DOI : 10.4153/CJM-1995-021-6
Mots-clés : 20E18, 20E36, 22C05 
Herfort, Wolfgang N.; Ribes, Luis; Zalesskii, Pavel A. Fixed Points of Automorphisms of Free Pro-p Groups of Rank 2. Canadian journal of mathematics, Tome 47 (1995) no. 2, pp. 383-404. doi: 10.4153/CJM-1995-021-6
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