Jacobians with prescribed eigenvectors

TL;DR

This paper characterizes all functions whose Jacobians have prescribed eigenvectors, using intrinsic PDE systems and generalized Frobenius theorems, with detailed analysis for involutive frames and specific cases.

Contribution

It introduces an intrinsic, coordinate-independent formulation of the eigenvector Jacobian problem and provides a comprehensive analysis of solution structures for involutive and non-involutive frames.

Findings

Complete analysis for involutive, rich frames.

Explicit solutions for the case m=3, arbitrary n.

Partial results for non-involutive frames in low dimensions.

Abstract

Let $\Omega\subset \mathbb{R}^n$ be open and let $\mathcal{R}$ be a partial frame on $\Omega$, that is a set of $m$ linearly independent vector fields prescribed on $\Omega$ ($m\leq n$). We consider the issue of describing the set of all maps $F:\Omega\to\mathbb{R}^n$ with the property that each of the given vector fields is an eigenvector of the Jacobian matrix of $F$. By introducing a coordinate independent definition of the Jacobian, we obtain an intrinsic formulation of the problem, which leads to an overdetermined PDE system, whose compatibility conditions can be expressed in an intrinsic, coordinate independent manner. To analyze this system we formulate and prove a generalization of the classical Frobenius integrability theorems. The size and structure of the solution set of this system depends on the properties of the partial frame, in particular, whether or not it is in involution. A particularly nice subclass of involutive partial frames, called rich, can be completely analyzed. Involutive, but non-rich case is somewhat harder to handle. We provide a complete answer in the case of $m=3$ and arbitrary $n$, as well as some general results for arbitrary $m$. The non-involutive case is far more challenging, and we only obtain a comprehensive analysis in the case $n=3$, $m=2$. Finally, we provide explicit examples illustrating the various possibilities. Our initial motivation for considering this problem comes from the geometric study of hyperbolic conservative systems in one spatial dimension.