In this paper we classify linear maps preserving commutativity in both directions on the space N(F) of strictly upper triangular (n + 1) x (n + 1) matrices over a field F. We show that for n greater than or equal to 3 a linear map phi on N(F) preserves commutativity in both directions if and only if phi = phi' + f where phi' is a product of standard maps on N(F) and f is a linear map of N(F) into its center. (C) 2002 Elsevier Science Inc. All rights reserved. [References: 16]
展开▼