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e^A (*A is a matrix)

• To: bappadit at ecn.purdue.edu, mathgroup at yoda.physics.unc.edu
• Subject: e^A (*A is a matrix)
• From: jcw at chem.ucsd.edu (John C Wheeler)
• Date: Mon, 16 Mar 92 14:43:34 -0800

Bappaditya Banerjee writes

>Does anybody have a routine to do e^A where A is atleast a 4 by 4 matrix ?

What about the "standard" procedure of writing A = MLM^-1 where L is the
diagaonal matrix of the eigenvalues of A and M is the matrix of eigenvecors?
Then  exp(A) = M exp(L) M^-1, where exp(L) is, of course just the diagonal
matrix with elements that are the exponentials of the eigenvalues.  This
reduces the problem to the "standard" one of finding eigenvalues and 
eigenvectors.

jcw at chem.UCSD.EDU (John C Wheeler)