On the analytical invariance of the semigroups of a quasi-ordinary hypersurface singularity

Abstract

We associate to any irreducible germ $\mathcal{S}$ of a complex quasi-ordinary hypersurface an analytically invariant semigroup. We deduce a direct proof (without passing through their embedded topological invariance) of the analytical invariance of the normalized characteristic exponents. These exponents generalize the generic Newton-Puiseux exponents of plane curves. Incidentally, we give a toric description of the normalization morphism of the germ $\mathcal{S}$.