English

Logrithmic Versions of Ginzburg's Sharp Operation for Free Divisors

Algebraic Geometry 2025-09-30 v2

Abstract

Let MM be a complex manifold, DMD\subset M a free divisor and U=MDU=M\setminus D its complement. In this paper we study the characteristic cycle CC(γ\indU)\textup{CC}(\gamma\cdot \ind_U) of the restriction of a constructible function γ\gamma on UU. We globalise Ginzburg's local sharp construction and introduce the log transversality condition, which is a new transversality condition about the relative position of γ\gamma and DD. We prove that the log transversality condition is satisfied if either DD is normal crossing and γ\gamma is arbitrary, or DD is holonomic strongly Euler homogheneous and γ\gamma is non-characteristic. Under the log transversality assumption we establish a logarithmic pullback formula for CC(γ\indU)\textup{CC}(\gamma\cdot \ind_U). Mixing Ginzburg's sharp construction with the logarithmic pullback, we obtain a double restriction formula for the Chern-Schwartz-MacPherson class c(γ\indDV)c_*(\gamma\cdot \ind_{D\cup V}) where VV is any reduced hypersurface in MM. Applications of our results include the non-negativity of Euler characteristics of effective constructible functions, and CSM classes of hypersurfaces in the open manifold PnD\mathbb{P}^n\setminus D when DD is a linear free divisor or a free hyperplane arrangement.

Keywords

Cite

@article{arxiv.2505.24236,
  title  = {Logrithmic Versions of Ginzburg's Sharp Operation for Free Divisors},
  author = {Xia Liao and Xiping Zhang},
  journal= {arXiv preprint arXiv:2505.24236},
  year   = {2025}
}

Comments

minor revision, submitted version