Jordan Block

A matrix, also called a canonical box matrix, having zeros everywhere except along the diagonal and superdiagonal, with each element of the diagonal consisting of a single number , and each element of the superdiagonal consisting of a 1. For example,

(Ayres 1962, p. 206).

Note that the degenerate case of a matrix is considered a Jordan block even though it lacks a superdiagonal to be filled with 1s (Strang 1988, p. 454).

A Jordan canonical form consists of one or more Jordan blocks.

The convention that 1s be along the subdiagonal instead of the superdiagonal is sometimes adopted instead (Faddeeva 1958, p. 50).