Multiplier ideals of normal surface singularities

TL;DR

This paper investigates the properties of multiplier ideals and jumping numbers in complex normal surface singularities, providing combinatorial formulas and extending known results to more general settings using Hodge spectra.

Contribution

It offers combinatorial methods to compute multiplicities of jumping numbers and extends Budur's results to complex surface singularities with new formulae.

Findings

Multiplicities are computable from resolution data and graphs.

Extended Budur's identification to complex surface singularities.

Explicit formulas for weighted homogeneous and splice quotient singularities.

Abstract

We study the multiplier ideals and the corresponding jumping numbers and multiplicities $\{m(c)\}_{c\in \mathbb{R}}$ in the following context: $(X,o)$ is a complex analytic normal surface singularity, ${\mathfrak a}\subset \mathcal{O}_{X,o}$ is an ${\mathfrak m}_{X,o}$--primary ideal, $\phi:\widetilde{X}\to X$ is a log resolution of $\mathfrak{a}$ such that $\mathfrak{a}\mathcal{O}_{\widetilde{X}}=\mathcal{O}_{\widetilde{X}}(-F)$, for some nonzero effective divisor $F$ supported on $\phi^{-1}(0)$. We show that $\{m(c)\}_{c>0}$ is combinatorially computable from $F$ and the resolution graph $\Gamma$ of $\phi$, and we provide several formulae. We also extend Budur's result (valid for $(X,o)=(\mathbb{C}^2,0)$), which makes an identification of $\sum_{c\in[0,1]}m(c)t^c$ with a certain Hodge spectrum. In our general case we use Hodge spectrum with coefficients in a mixed Hodge module. We show that $\{m(c)\}_{c\leq 0}$ usually depends on the analytic type of $(X,o)$. However, for some distinguished analytic types we determine it concretely. E.g., when $(X,o)$ is weighted homogeneous (and $F$ is associated with the central vertex), we recover $\sum_cm(c)t^c$ from the Poincar\'e series of $(X,o)$ and when $(X,o)$ is a splice quotient then we recover $\sum_cm(c)t^c$ from the multivariable topological Poincar\'e (zeta) function of $\Gamma$.