- #1
TheMercury79
- 24
- 5
- Homework Statement
- I was wondering the same thing as the poster of this original thread:
https://www.physicsforums.com/threads/cubing-a-matrix.451979/
I have a matrix that needs to be cubed, so which order should I use:
[A]^3 = [A]^2[A] or [A][A]^2 ?
- Relevant Equations
- The two people that answered both say the order doesn't matter since
matrix multiplication is associative:
(A*A)*A=A*(A*A)
But I actually don't get the same matrix. What I get is the transpose of the other when I change the order
i.e when I do [A]^2[A] I get the transpose of [A][A]^2 and vice versa
What I'm trying to do is find the cube of the expectation value of x in the harmonic oscillator in matrix form.
We're supposed to use direct matrix multiplication (using ladder operators is in part b of the problem).
I seem to have got the correct matrix elements for x^2, but for x^3 the order of the multiplication does seem
to matter.
i.e when I do [A]^2[A] I get the transpose of [A][A]^2 and vice versa
What I'm trying to do is find the cube of the expectation value of x in the harmonic oscillator in matrix form.
We're supposed to use direct matrix multiplication (using ladder operators is in part b of the problem).
I seem to have got the correct matrix elements for x^2, but for x^3 the order of the multiplication does seem
to matter.