Characteristic cycle of an L-adic sheaf
The characteristic cycle of an L-adic sheaf on a smooth variety over a perfect field is a Z-linear combination of irreducible components of the singular support, defined by Beilinson as a closed conical subset of the cotangent bundle. It is an algebraic analogue of that studied by Kashiwara and Schapira in a transcendental setting. We discuss its functorial property with respect to proper direct image.