Overdiagonal subgroups of the hyperbolic unitary group for a good form ring over a field
Let \((R,\Lambda)\) be a form ring over a field \(R\), \(R_0\) the subfield of \(R\) consisting of all elements fixed by the involution, and \(U(2n,R,\Lambda)\) the hyperbolic unitary group. The author proves that, if \(\text{card }R\geq 13\) and \(\text{card }R_0\geq 7\), then the lattice of subgroups of \(U(2n,R,\Lambda)\) that contain all diagonal unitary matrices allows the standard description except for the symplectic group over a field of characteristic \(2\) and the defective orthogonal groups.
scientific article; zbMATH DE number 1337569