ThesisAuthors: Carter, Andrea C. (2006)
Let S1 be a Del Pezzo surface of degree one over a number field k, and let S1 denote the base-change of S1 over the algebraic closure k of k. We establish a criterion for the existence of a non-trivial element of order five in the Brauer group of S1 in terms of certain Galois stable configurations of exceptional divisors on this surface. 
