Displaying similar documents to “Higher order Ossermann pseudo-Riemannian manifolds of neutral signature ( 2 , 2 ) .”

Nilpotent complex structures.

Luis A. Cordero, Marisa Fernández, Alfred Gray, Luis Ugarte (2001)



Este artículo presenta un panorama de algunos resultados recientes sobre estructuras complejas nilpotentes J definidas sobre nilvariedades compactas. Tratamos el problema de clasificación de nilvariedades compactas que admiten una tal J, el estudio de un modelo minimal de Dolbeault y su formalidad, y la construcción de estructuras complejas nilpotentes para las cuales la sucesión espectral de Frölicher no colapsa en el segundo término.

Group rings with FC-nilpotent unit groups.

Vikas Bist (1991)

Publicacions Matemàtiques


Let U(RG) be the unit group of the group ring RG. Groups G such that U(RG) is FC-nilpotent are determined, where R is the ring of integers Z or a field K of characteristic zero.

On Kolchin's theorem.

Israel N. Herstein (1986)

Revista Matemática Iberoamericana


A well-known theorem due to Kolchin states that a semi-group G of unipotent matrices over a field F can be brought to a triangular form over the field F [4, Theorem H]. Recall that a matrix A is called unipotent if its only eigenvalue is 1, or, equivalently, if the matrix I - A is nilpotent. Many years ago I noticed that this result of Kolchin is an immediate consequence of a too-little known result due to Wedderburn [6]. This result of Wedderburn asserts that if B is a finite...