Normisomorphismen und Normkurven endlichdimensionaler projektiver Desargues-Räume.
On the geometry of field extensions.
On the matrices of central linear mappings
We show that a central linear mapping of a projectively embedded Euclidean -space onto a projectively embedded Euclidean -space is decomposable into a central projection followed by a similarity if, and only if, the least singular value of a certain matrix has multiplicity . This matrix is arising, by a simple manipulation, from a matrix describing the given mapping in terms of homogeneous Cartesian coordinates.
From geometry to invertibility preservers
We characterize bijections on matrix spaces (operator algebras) preserving full rank (invertibility) of differences of matrix (operator) pairs in both directions.
Symplectic Plücker transformations.
Radical parallelism on projective lines and non-linear models of affine spaces.
The connected components on the projective line over a ring.
Quadratic embeddings.
The Betten-Walker spread and Cayley's ruled cubic surface.
Factor-group-generated polar spaces and (multi-)qudits.
The Veldkamp space of two-qubits.
Twin “Fano-snowflakes” over the smallest ring of ternions.
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