Lifting zero-dimensional schemes and divided powers

Abstract

We study divided power structures on finitely generated $k$-algebras, where $k$ is a field of positive characteristic $p$. As an application we show examples of $0$-dimensional Gorenstein $k$-schemes that do not lift to a fixed noetherian local ring of non-equal characteristic. We also show that Frobenius neighbourhoods of a singular point of a general hypersurface of large dimension have no liftings to mildly ramified rings of non-equal characteristic.

v2: various changes, added interesting Example 4.3, 12 pages, to appear in Bull. Lond. Math. Soc