Bi-Lipschitz Invariants in Singularity Theory: Lojasiewicz Exponent, Multiplicity, and Euler Obstruction
Amanda S. Araujo, T. M. Dalbelo, Thiago da Silva
TL;DR
This work investigates whether key local invariants in singularity theory—Lojasiewicz exponent, multiplicity, and Euler obstruction—are preserved under bi-Lipschitz equivalence. Building on Bivià-Ausina and Fukui's framework, it extends to ideals on analytic spaces and proves that the Lojasiewicz exponent and order are invariant, and that multiplicity is preserved under bi-Lipschitz maps when the ideal closure equals a power of the maximal ideal. It also provides a partial positive answer to the bi-Lipschitz invariance of the local Euler obstruction for hypersurfaces with isolated singularities under non-degeneracy and toric-type conditions. These results bridge metric geometry with algebraic invariants and connect Zariski-type questions with toric and Newton polyhedron techniques.
Abstract
In this work, we investigate the bi-Lipschitz invariance of three fundamental local invariants in singularity theory: the Lojasiewicz exponent, the Hilbert-Samuel multiplicity, and the local Euler obstruction. We draw inspiration from Bivia-Ausina and Fukui, whose framework we extend to ideals in analytic spaces. We establish conditions under which these invariants remain unchanged under bi-Lipschitz equivalence. In particular, we prove a special case of the metric version of Zariski multiplicity conjecture. We show that multiplicity is preserved when the ideal coincides with the integral closure of its order ideal. We also provide a partial answer to the open question of whether the local Euler obstruction is a bi-Lipschitz invariant. For hypersurfaces with isolated singularities, we show that the Euler obstruction is preserved under non-degeneracy conditions. These results contribute to the understanding of metric invariants in complex analytic geometry.