On an ideal membership problem

Abstract

Suppose $f_1,\dots ,f_{n+1}$ are elements of a regular ring $R$, where $n:=\dim R$. The first author proved that $f_1^n\cdots f_{n+1}^n\in (f_1^{n+1},\dots ,f_{n+1}^{n+1})R$; this uses the Brian\c con-Skoda theorem --- no simpler proof is known, as far as we are aware. We show here that this result is optimal in many respects. On the other hand, when the $f_i$ are homogeneous general polynomials of a fixed degree in $R:=\mathbb{F}[x_1,\dots ,x_n]$, for $\mathbb{F}$ a field of characteristic zero, we prove that $f_1\cdots f_{n+1}\in (f_1^2,\dots ,f_{n+1}^2)R$.

Preliminary version