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Valuations and Plurisubharmonic SingularitiesSébastien Boucksom, Charles Favre and Mattias Jonsson (1) Institut de Mathématiques, CNRS-Université Paris 6, 75251, Paris CEDEX 05, France
(2) CNRS-CMLS, École Polytechnique, Route de Saclay, 91128, Palaiseau Cedex, France
(3) Department of Mathematics, University of Michigan, MI 48109-1043, Ann Arbor, USA
We extend to higher dimensions some of the valuative analysis of singularities of plurisubharmonic (psh) functions developed by the ﬁrst two authors. Following Kontsevich and Soibelman we describe the geometry of the space V of all normalized valuations on C[x1 , . . . , xn] centered at the origin. It is a union of simplices naturally endowed with an affine structure. Using relative positivity properties of divisors living on modiﬁcations of Cn above the origin, we deﬁne formal psh functions on V, designed to be analogues of the usual psh functions. For bounded formal psh functions on V, we deﬁne a mixed Monge–Ampère operator which reﬂects the intersection theory of divisors above the origin of Cn. This operator associates to any (n − 1)-tuple of formal psh functions a positive measure of ﬁnite mass on V. Next, we show that the collection of Lelong numbers of a given germ u of a psh function at all inﬁnitely near points induces a formal psh function û on V. When φ is a psh Hölder weight in the sense of Demailly, the generalized Lelong number νφ(u) equals the integral of û against the Monge–Ampère measure of φ^. In particular, any generalized Lelong number is an average of valuations. We also show how to compute the multiplier ideal of u and the relative type of u with respect to φ in the sense of Rashkovskii, in terms of û and φ^.
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Boucksom Sébastien, Favre Charles, Jonsson Mattias: Valuations and Plurisubharmonic Singularities. Publ. Res. Inst. Math. Sci. 44 (2008), 449-494. doi: 10.2977/prims/1210167334