Embedding codimension of the space of arcs

Abstract

We introduce a notion of embedding codimension of an arbitrary local ring, establish some general properties, and study in detail the case of arc spaces of schemes of finite type over a field. Viewing the embedding codimension as a measure of singularities, our main result can be interpreted as saying that the singularities of the arc space are maximal at the arcs that are fully embedded in the singular locus of the underlying scheme, and progressively improve as we move away from said locus. As an application, we complement a theorem of Drinfeld, Grinberg, and Kazhdan on formal neighborhoods in arc spaces by providing a converse to their theorem, an optimal bound for the embedding codimension of the formal model appearing in the statement, a precise formula for the embedding dimension of the model constructed in Drinfeld's proof, and a geometric meaningful way of realizing the decomposition stated in the theorem.

arXiv commentv2: 38 pages, minor changes following the referee's report. To appear in Forum of Mathematics, Pi

References in corpus (7)

• Germs of arcs on singular algebraic varieties and motivic integration
• On the formal arc space of a reductive monoid
• On the Grinberg - Kazhdan formal arc theorem
• Jacobian discrepancies and rational singularities
• Differentials on the arc space
• Grinberg-Kazhdan theorem and Newton groupoids
• Weierstrass preparation theorem and singularities in the space of non-degenerate arcs