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Published online by Cambridge University Press: 09 April 2009
Profinite groups (that is, compact totally disconnected topological groups) have been characterized as Galois groups in Krakowski (1971) and Leptin (1955). They can, in fact, be realized as groups of permutations on sets of transcendentals where every transcendental has a finite orbit under the group action and the fixed field is generated by the invariant rational functions on these orbits. If G = {G←x ¦ α∈A} we define the cardinality of G as ¦ G¦ = ¦A¦. In this paper we construct, for every cardinal number c and profinite group G with ¦G¦ ≦ c two universal fields kc and Kc so that G ≃ Gal (KcKG) and G ≃ (KGKc) for fields KG and kG which depend on G. See Cassels and Frohlich (1967) for a description of the basic properties of profinite groups.