2026/06/25 by Maria Dronka
Mathematics · #math.RA #msc:15A18 #msc:15A21 #msc:15A22
21 pages, 2 figures
arxiv created 2026/06/25 · arxiv updated 2026/07/31
We study matrix pencils of the form λE - (J-R)Q, where Q^*E = E^*Q ≥ 0, J^* = -J, R^* = R ≥ 0, and λE - Q is regular, in the framework of Pokrzywa's ordering of strict equivalence orbits. We characterise the maximal elements, analyse some properties of the orbit closures, and derive a restriction on possible degenerations when Q = I. We also consider the case where λE - Q may be singular, which naturally arises in the study of orbit closures, and obtain a partial result on the Kronecker canonical form. The theory is illustrated by numerous examples.