Bertini theorems for differential algebraic geometry

TL;DR

This paper establishes a differential analogue of Bertini's theorem, showing that generic hypersurface sections of differential algebraic varieties are irreducible and of codimension one, extending classical intersection theory into differential algebraic geometry.

Contribution

It proves the differential Bertini's theorem for arbitrary affine differential algebraic varieties and computes Kolchin polynomials for their intersections.

Findings

Generic differential hypersurface sections are irreducible and of codimension one.

Stronger results for hypersurfaces of order at least one.

Calculated Kolchin polynomials for intersections.

Abstract

We study intersection theory for differential algebraic varieties. Particularly, we study families of differential hypersurface sections of arbitrary affine differential algebraic varieties over a differential field. We prove the differential analogue of Bertini's theorem, namely that for an arbitrary geometrically irreducible differential algebraic variety which is not an algebraic curve, generic hypersurface sections are geometrically irreducible and codimension one. Surprisingly, we prove a stronger result in the case that the order of the differential hypersurface is at least one; namely that the generic differential hypersurface sections of an irreducible differential algebraic variety are irreducible and codimension one. We also calculate the Kolchin polynomials of the intersections and prove several other results regarding intersections of differential algebraic varieties.