On the Fukui-Kurdyka-Paunescu Conjecture

TL;DR

This paper proves the Fukui-Kurdyka-Paunescu Conjecture, demonstrating that certain bi-Lipschitz homeomorphisms preserve multiplicities of real and complex analytic sets, and extends these invariance results globally and to algebraic sets.

Contribution

The paper confirms the conjecture for subanalytic arc-analytic bi-Lipschitz homeomorphisms and extends invariance of multiplicity and degree to global and algebraic contexts.

Findings

Proved the Fukui-Kurdyka-Paunescu Conjecture.

Established invariance of multiplicity under specific bi-Lipschitz homeomorphisms.

Extended invariance results to global and algebraic cases.

Abstract

In this paper, we prove Fukui-Kurdyka-Paunescu's Conjecture, which says that subanalytic arc-analytic bi-Lipschitz homeomorphisms preserve the multiplicities of real analytic sets. We also prove several other results on the invariance of the multiplicity (resp. degree) of real and complex analytic (resp. algebraic) sets. For instance, still in the real case, we prove a global version of Fukui-Kurdyka-Paunescu's Conjecture. In the complex case, one of the results that we prove is the following: If $(X,0)\subset (\mathbb{C}^n,0), (Y,0)\subset (\mathbb{C}^m,0)$ are germs of analytic sets and $h\colon (X,0)\to (Y,0)$ is a semi-bi-Lipschitz homeomorphism whose graph is a complex analytic set, then the germs $(X,0)$ and $(Y,0)$ have the same multiplicity. One of the results that we prove in the global case is the following: If $X\subset \mathbb{C}^n, Y\subset \mathbb{C}^m$ are algebraic sets and $\phi\colon X\to Y$ is a semialgebraic semi-bi-Lipschitz homeomorphism such that the closure of its graph in $\mathbb{P}^{n+m}(\mathbb{C})$ is an orientable homological cycle, then ${\rm deg}(X)={\rm deg}(Y)$.