A gamma sheaf is a certain l-adic sheaf on a reductive group defined over a finite field which generalizes the classical Artin-Schreier sheaf. In my talk I will explain the motivation and the proof of the acyclicity of such gamma sheaves for general linear groups. This result is originally conjectured by Braverman-Kazhdan, the proof is joint work with B. C. Ngo. Speaker(s): Shuyang Cheng (University of Michigan)