Abstract: Let p be an odd prime number and let S be a finite set of prime numbers congruent to 1 modulo p. We prove that the group G_S(Q)(p) has cohomological dimension 2 if the linking diagram attached to S and p satisfies a certain technical condition, and we show that G_S(Q)(p) is a duality group in these cases. Furthermore, we investigate the decomposition behaviour of primes in the extension Q_S(p)/Q and we relate the cohomology of G_S(Q)(p) to the étale cohomology of the scheme Spec(Z)-S. Finally, we calculate the dualizing module. |

** ** Preprint pdf-file ** **
circular.pdf (version of 5.2.06; typo-corrected)