# Thread: Self outer product of a matrix

1. ## Self outer product of a matrix

Hi

How can we find the self outer product of matrix A?

$A=\begin{pmatrix}1&2&3\\4&5&6\end{pmatrix}$

Thanks

2. Originally Posted by dimper129
Hi

How can we find the self outer product of matrix A?

$A=\begin{pmatrix}1&2&3\\4&5&6\end{pmatrix}$

Thanks

I'm afraid "self outer product" is not a common name for something in mathematics: what is it, exactly?

Tonio

3. The "outer product" of two n vectors is an n by n matrix and the tensor product (where two n by n tensor produce and "n by n by n by n" tensor) is often called an "outerproduct" so, at a guess, the "outer product" of two matrices written as n by m and j by k arrays is an n by m by j by k array (written in four dimensions, of course!) where the $a_{mnij}$ entry is $A_{ij}B_{jk}$.

That makes the calculation of this "outerproduct" easy but I'm not sure how one would represent that in 2D (on the screen).

4. Thank you