Circular sets of primes of imaginary quadratic number fields

Abstract

Let p be an odd prime number and let K be an imaginary
quadratic number field whose class number is not divisible by p. For a set S of primes of K whose norm is congruent to 1 modulo p, we introduce the notion of strict circularity. We show that if S is strictly circular, then the group G(KS(p)=K) is of cohomological dimension 2 and give some explicit examples.