Published online by Cambridge University Press: 09 June 2017
We investigate images of higher-order differential operators of polynomial algebras over a field $k$. We show that, when $\operatorname{char}k>0$, the image of the set of differential operators $\{\unicode[STIX]{x1D709}_{i}-\unicode[STIX]{x1D70F}_{i}\mid i=1,2,\ldots ,n\}$ of the polynomial algebra $k[\unicode[STIX]{x1D709}_{1},\ldots ,\unicode[STIX]{x1D709}_{n},z_{1},\ldots ,z_{n}]$ is a Mathieu subspace, where $\unicode[STIX]{x1D70F}_{i}\in k[\unicode[STIX]{x2202}_{z_{1}},\ldots ,\unicode[STIX]{x2202}_{z_{n}}]$ for $i=1,2,\ldots ,n$. We also show that, when $\operatorname{char}k=0$, the same conclusion holds for $n=1$. The problem concerning images of differential operators arose from the study of the Jacobian conjecture.
This work was supported by the NSF of China (11401249, 11371165) and the STDPF of Jilin Province, China (20150520051JH, 20150101001JC).