Integration over the space of functions and Poincar´e series: a revision

Abstract

Earlier (2000) the authors introduced the notion of the integral with respect to the Euler characteristic over the space of germs of functions on a variety and over its projectivization. This notion permitted to rewrite in new terms known definitions and statements and also appeared to be an effective tool to compute Poincar´e series of multi-index filtrations in some situations. However the “classical” (initial) notion can be applied only to multi-index filtrations defined by so-called finitely determined valuations (or order functions). Here we introduce a modified version of the notion of the integral with respect to the Euler characteristic over the projectivization of the space of function germs. This version can be applied in a number of settings where the “classical approach” does not work. We give examples of application of this concept for definitions and computations of the Poincar´e series of collections of plane valuations which include valuations not centred at the origin, including equivariant ones.