Tannaka’s theorem (cf. [19]) states that a linear algebraic group is determined by its category of representations. The problem of recognizing when a category is the category of representations of a linear algebraic group (or, more generally, an affine group scheme) is attacked via the theory of neutral Tannakian categories (see [18], [9]). This theory allows one to detect the underlying presen...

The spatial discretization of the magnetic vector potential formulation of magnetoquasistatic field problems results in an infinitely stiff differential-algebraic equation system. It is transformed into a finitely stiff ordinary differential equation system by applying a generalized Schur complement. Applying the explicit Euler time integration scheme to this system results in a small maximum s...

An extension of the finite element method–flux corrected transport stabilization for hyperbolic problems in the context of partial differential–algebraic equations is proposed. Given a local extremum diminishing property of the spatial discretization, the positivity preservation of the one-step θ-scheme when applied to the time integration of the resulting differential–algebraic equation is sho...

We discuss new discretization methods for linear differential–algebraic equations with variable coefficients. We introduce numerical methods to compute the local invariants of such differential–algebraic equations that were introduced by the authors in a previous paper. Using these quantitities we are able to determine numerically global invariances like the strangeness index, which generalizes...