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Transpose

The object obtained by replacing all elements $a_{ij}$ with $a_{ji}$. For a second-Rank Tensor $a_{ij}$, the tensor transpose is simply $a_{ji}$. The matrix transpose, written ${\hbox{\sf A}}^{\rm T}$, is the Matrix obtained by exchanging A's rows and columns, and satisfies the identity

\begin{displaymath}
({\hbox{\sf A}}^{\rm T})^{-1}=({\hbox{\sf A}}^{-1})^{\rm T}.
\end{displaymath}

The product of two transposes satisfies
$\displaystyle ({\hbox{\sf B}}^{\rm T}{\hbox{\sf A}}^{\rm T})_{ij}$ $\textstyle =$ $\displaystyle (b^{\rm T})_{ik}(a^{\rm T})_{kj} = b_{ki}a_{jk} = a_{jk}b_{ki} = ({\hbox{\sf A}}{\hbox{\sf B}})_{ji}$  
  $\textstyle =$ $\displaystyle ({\hbox{\sf A}}{\hbox{\sf B}})^{\rm T}_{ij}.$  

Therefore,

\begin{displaymath}
({\hbox{\sf A}}{\hbox{\sf B}})^{\rm T} = {\hbox{\sf B}}^{\rm T}{\hbox{\sf A}}^{\rm T}.
\end{displaymath}




© 1996-9 Eric W. Weisstein
1999-05-26