0
$\begingroup$

Consider a 3*3 matrix $\left( \begin{array}{*{20}{c}} {{m_{11}}}&{{m_{12}}}&{{m_{13}}}\\ {{m_{21}}}&{{m_{22}}}&{{m_{23}}}\\ {{m_{31}}}&{{m_{32}}}&{{m_{33}}} \end{array} \right)$ and its permutation group, which consists of all the possible permutation over its element such as $\left( {{m_{22}},{m_{33}}} \right) \cdot \left( {{m_{11}},{m_{21}},{m_{32}}} \right)$. I wonder whether all these permutations can be expressed as a composition of several row permutation and column permutation? If so, does it still hold when we consider a non-square matrix?

$\endgroup$
1
  • $\begingroup$ If I understand your question correctly, the answer is no. As you have defined it, there are $9!$ elements in your permutation group, but there are only $6$ permutation matrices. $\endgroup$
    – Tony Huynh
    Apr 23, 2019 at 9:50

1 Answer 1

1
$\begingroup$

Of course not, for the following reason. When applying either a row or a column permutation, then the set of products $$m_{1\sigma(1)}\cdots m_{n\sigma(n)},\qquad\sigma\in\frak{S}_n$$ is unchanged. On the contrary, if you apply another permutation of the entries, this becomes false. For instance, if you apply the transposition $(m_{22},m_{33})$, then the product $m_{12}m_{21}m_{33}$ becomes $m_{12}m_{21}m_{22}$.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.