Jørgen Vold Rennemo (University of Oslo)
A cohomology class of a smooth complex variety of dimension n is said to be of coniveau at least c if it vanishes on the complement of a closed subvariety of codimension at least c, and of strong coniveau at least c if it comes about by proper pushforward from the cohomology of a smooth variety of dimension at most n–c. The notions of coniveau and strong coniveau each define a filtration on the cohomology groups of a variety. These filtrations are known to coincide in many cases, but Benoist and Ottem have recently given examples to show that they differ in general. I will tell that story and explain a construction of some new examples where the filtrations differ, which are found in joint work with John Christian Ottem.