7 citations · 14 across the 11 of their papers we have counts for
11 papers
Confluence Graphs of Unitals
Theo Grundhöfer, Markus J. Stroppel, Hendrik Van Maldeghem
We show that the cliques of maximal size in the confluence graph of an arbitrary unital of order have size , and that these cliques are the pencils of all blocks through…
Semiaffine stable planes
Rainer Löwen, Markus Johannes Stroppel
A locally compact stable plane of positive topological dimension will be called semiaffine if for every line and every point not in there is at most one line passing th…
An isomorphism of unitals, and an isomorphism of classical groups
Markus Johannes Stroppel
An isomorphism between two hermitian unitals is proved, and used to treat isomorphisms of classical groups that are related to the isomorphism between certain simple real Lie algeb…
Subalgebras of Octonion Algebras
Norbert Knarr, Markus J. Stroppel
For an arbitrary octonion algebra, we determine all subalgebras. It turns out that every subalgebra of dimension less than four is associative, while every subalgebra of dimension…
Hodge Operators and Exceptional Isomorphisms between Unitary Groups
Linus Kramer, Markus J. Stroppel
We give a generalization of the Hodge operator to spaces endowed with a hermitian or symmetric bilinear form over arbitrary fields, including the characteristic two cas…
Hodge operators and groups of isometries of diagonalizable symmetric bilinear forms in characteristic two
Linus Kramer, Markus J. Stroppel
We study groups of isometries on non-alternating symmetric bilinear forms on vector spaces of characteristic two, and actions of these groups on exterior powers of the space, viewe…
Unitals with many involutory translations
Theo Grundhöfer, Markus J. Stroppel, Hendrik Van Maldeghem
If every point of a unital is fixed by a non-trivial translation and at least one translation has order two then the unital is classical (i.e., hermitian).
Finite subunitals of the Hermitian unitals
Theo Grundhöfer, Markus J. Stroppel, Hendrik Van Maldeghem
Every finite subunital of any generalized hermitian unital is itself a hermitian unital; the embedding is given by an embedding of quadratic field extensions. In particular, a gene…
Moufang sets generated by translations in unitals
Theo Grundhöfer, Markus J. Stroppel, Hendrik Van Maldeghem
We consider unitals of order with two points which are centers of translation groups of order . The group generated by these translations induces a Moufang set on the bl…
Kernels of Linear Representations of Lie Groups, Locally Compact Groups, and Pro-Lie Groups
Markus Stroppel
For a topological group G the intersection KO(G) of all kernels of ordinary representations is studied. We show that KO(G) is contained in the center of G if G is a connected pro-L…
Stabilizers of Subspaces under Similitudes of the Klein Quadric, and Automorphisms of Heisenberg Algebras
Michael Gulde, Markus Stroppel
We determine the groups of automorphisms and their orbits for nilpotent Lie algebras of class 2 and small dimension, over arbitrary fields (including the characteristic 2 case).