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[Axiom-developer] evaluate a polynom for a matrix.

From: Francois Maltey
Subject: [Axiom-developer] evaluate a polynom for a matrix.
Date: 01 Apr 2007 18:57:44 +0200
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4


Let P in Ring[X] and M in SquareMatrix(Ring)

The mathematics evaluate P(M) 
   by sum (ak*M^k, k=0..deg P) in SquareMatrix(Ring)
where P = sum (ak*X^k, k=0..deg P)

How can I do this in axiom.

Maple fails in the subs command of a*M^2 + b*M + c 
because (a*M^2 + b*M) is a matrix, and c is a number.

Mupad could do it.

How can I do it with axiom ?

I have the beginning of the Caley-Hamilton theorem :
Now I must compute P(M) and find the zero matrix for n=1,2,3,4,5.

-- Create a generic matrix  

matriceN1 := n +-> _
  matrix [[("a".(i::String).(j::String))::Symbol for j in 1..n] for i in 1..n]
matriceN2 n ==
  matrix [[("a".(i::String).(j::String))::Symbol for j in 1..n] for i in 1..n]
M4 := matriceN2 4
-- Create an identity matrix 

(matrice N1 4)^0

zeroOrOne := b +-> if b then 1 else 0 
matriceId1 := n +-> _
  matrix [[zeroOrOne ((i=j)::Boolean) for j in 1..n] for i in 1..n]
matriceId1 4

matriceId2 := n +-> diagonalMatrix [1 for k in 1..n] 
matriceId2 5 

coeff := (i, j) +-> if i=j then 1 else 0 
matriceId3 := n +-> matrix [[coeff (i,j) for i in 1..n] for j in 1..n]
matriceId3 4 

-- Computes determinant (M - x*Id) where M is the previous generic matrix

polCar := M +-> determinant (M - x * matriceId2 ncols M)
polCarN := n +-> polCar matriceN1 n
polCarN 2
P4 := polCarN 4

-- Now evaluate P4(M4). We might find the (0)_4 matrix.

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