Pluckerians twisted with linear forms and Druzkowski maps

Abstract

Let $C$ be an $n\times n$ matrix such that $ 3\leq n\leq 2\, \mathrm{rank}\,C$ and $T$ be the cubic linear map with respect to $C$. We introduce and apply an algebraic construction (called Pl$\ddot{\mathrm{u}}$cker polynomials) to show that if the Jacobian determinant of $T$ is constant, then the row matroid of $C$ is non-uniform, and the condition $3\leq n\leq 2\, \mathrm{rank}\,C$ can not be relaxed. This is one step forward from the fundamental $J(T)$=const$\Longrightarrow\det C=0$ constraint, and the key ingredient in the proof is the interplay between the standard \pkk relation and an unexpected linear rigidity phenomenon obtained via the Pl$\ddot{\mathrm{u}}$cker polynomials. We also exhibit independent interests of these polynomials as a variation of the classical Pl$\ddot{\mathrm{u}}$cker-Grassmann construction.