On the size of the genus of a division algebra

Abstract

Let D be a central division algebra of degree n over a field K. One defines the genus gen(D) as the set of classes [D′] ∈ Br(K) in the Brauer group of K represented by central division algebras D′ of degree n over K having the same maximal subfields as D. We prove that if the field K is finitely generated and n is prime to its characteristic, then gen(D) is finite, and give explicit estimations of its size in certain situations.