Constructing a derived zeta function
Constructing a derived zeta function
The local zeta function of a variety X over a finite field k can be defined to be ∑n≥1|(SymnX)(k)|tn. As this depends only on the point counts of symmetric powers of X it is an invariant of the class of X in the Grothendieck ring of varieties K0(Vark): the ring which is generated by varieties over k modulo the relation that whenever Z is a closed subvariety of Y we have [Y]=[Z]+[Y∖Z]. In fact, the local zeta function can be thought of as having codomain in the big WItt ring. Both the Grothendieck ring of varieties and the Witt ring appear as the 0-th K-theory groups of certain categories. In this talk we show how to lift the zeta function to K-theory to produce a map of spaces whose π0 is the local zeta function and use this map to find interesting elements in higher K-groups corresponding to the Grothendieck ring of varieties.