The period-index problem and arithmetic geometry
Max Lieblich, Brown University

The Brauer group has a habit of popping up throughout mathematics. Originally devised to classify certain finite-dimensional algebras over a field, the Brauer group has gradually revealed itself to be intimately related to modern algbraic and arithmetic geometry. It appears in contexts ranging from physics to number theory, and it lies at the heart of the Tate-Shafarevich conjecture.

Progress in understanding the Brauer group has often come in the form of a deeper understanding of its geometric properties. We will sketch the historical development of the Brauer group and describe some of its hidden ties to geometry, culminating in a recent result of de Jong on Brauer groups of surfaces and a related result for surfaces over finite fields. The methods we describe replace de Jong's original proof with ideas related to his Porter lectures. In the finite field case, different (but closely related) methods are required. This talk is intended for a general audience.