Matrix equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg53862] Matrix equations*From*: Jamie Vicary <jamievicary at gmail.com>*Date*: Tue, 1 Feb 2005 04:08:12 -0500 (EST)*Organization*: University of Cambridge, England*Sender*: owner-wri-mathgroup at wolfram.com

Hi there, I'm using Mathematica 5.1 and trying to solve equations like the following: A.{{1,0},{0,2}} == -{{1,0},{0,2}}.A i.e. I want to find the matrix that anticommutes with {{1,0},{0,2}}. The only matrix that solves this is the zero matrix {{0,0},{0,0}} but Mathematica refuses to solve the above equation for A, giving the usual "The equations appear to involve the variables to be solved for in an essentially non-algebraic way." If I set A={{a,b},{c,d}} and then solve the above equation for {{a,b},{c,d}} then Mathematica correctly tells me {{a->0, b->0, c->0, d->0}}, but this isn't what I want. I want to give Mathematica equations in terms of matrices, not in terms of their components. In summary: why, when I give Mathematica the above equation to solve for A, does it not solve it giving A->{{0,0},{0,0}} which is the trivial, unique solution to the equation? Thanks, Jamie Vicary.