A NEW CHARACTERIZATION OF THE CLOSEDNESS OF THE SUM OF TWO SUBSPACES

In this article, a new characterization of the closedness of the sum of two closed subspaces of a Hilbert space is established.

A Certain Kind of Non-Degenerate Solvable Lie Algebra on C

This paper deals with the non-degenerate solvable Lie algebra. They are divided into the direct sum of root subspaces under certain conditions. Some properties of these subspaces are shown in this paper.