Canonical Jordan block structure conjecture for regular differential-algebraic equations

Let E,F:IRm×mE,F:\mathcal I\rightarrow\mathbb{R}^{m\times m} be sufficiently smooth, and let {E,F}\{E,F\} be a regular pair with index μ2\mu\geq 2. Write rr for the dimension of the differential part and θ0θμ2>θμ1=0\theta_0\geq\cdots\geq\theta_{\mu-2}>\theta_{\mu-1}=0 for its characteristic values. In strong standard canonical form, let NN denote the nilpotent matrix associated with the algebraic part. Canonical Jordan block structure conjecture. The pair {E,F}\{E,F\} is transformable into strong standard canonical form, and the Jordan normal form of NN consists exactly of

mrθ0m-r-\theta_0

Jordan blocks of order 11,

θ0θ1\theta_0-\theta_1

Jordan blocks of order 22, continuing with

θμ3θμ2\theta_{\mu-3}-\theta_{\mu-2}

Jordan blocks of order μ1\mu-1, and

θμ2\theta_{\mu-2}

Jordan blocks of order μ\mu. This conjecture would provide a canonical justification for the characteristic values of regular differential-algebraic equations beyond the constant-matrix case; its status is not determined by the supplied text.

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Primary source

Diana Estévez Schwarz, René Lamour and Roswitha März, “The common ground of DAE approaches. An overview of diverse DAE frameworks emphasizing their commonalities”, arXiv:2412.15866 (2024).

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