Exponential complexes, period morphisms, and characteristic classes

Abstract

We introduce exponential complexes of sheaves on manifolds. They are resolutions of the (Tate twisted) constant sheaves of the rational numbers, generalising the short exact exponential sequence. There are canonical maps from the exponential complexes to the de Rham complex. Using this, we introduce new complexes calculating the rational Deligne cohomology. We call them exponential Deligne complexes. Their advantage is that, at least at the generic point of a complex variety, one can define Beilinson's regulator map to the rational Deligne cohomology on the level of complexes. Namely, we define period morphisms. We use them to produce homomorphisms from motivic complexes to the exponential Deligne complexes at the generic point. Combining this with the construction of Chern classes with coefficients in the bigrassmannian complexes, we get, for the weights up to four, local explicit formulas for the Chern classes in the rational Deligne cohomology via polylogarithms.