High Quality Content by WIKIPEDIA articles! In algebraic geometry, the Fourier Deligne transform, or l-adic Fourier transform, or geometric Fourier transform, is an operation on objects of the derived category of l-adic sheaves over the affine line. It was introduced by Pierre Deligne in 1976-11-29 in a letter to David Kazhdan as an analogue of the usual Fourier transform. It was used by Laumon (1987) to simplify Deligne's proof of the Weil conjectures.