Bertini theorems for Hilbert-Samuel multiplicity over finite fields

Abstract

Let $X\subseteq \mathbb{P}^n_{\mathbb{F}_q}$ be a reduced, equidimensional, quasiprojective scheme. We prove that there exists a positive-density set of hypersurfaces $H_f$ such that for every closed point $P\in X\cap H_f$, one has $\mathrm{ord}_P(f)=1$ and $e_P(X\cap H_f)=e_P(X)$.