Unramified Brauer groups of finite simple groups of Lie type $A_{\ell }$

Fedor Bogomolov, Jorge Maciel, Tihomir Petrov

We study the subgroup B_0(G) of H^2(G,Q/Z) consisting of all elements which have trivial restrictions to every Abelian subgroup of G. The group B_0(G) serves as the simplest nontri…