Title says it all.

Is there any specific operator symbol for matrix multiplication?

Not just write down side by side but symbols like cross ($\times$).

  • 1
    $\begingroup$ Ehm, just a small dot perhaps? I just checked a book for you and that's what they do. Sometimes when matrices are given capital letters, they don't write anything, so AB implies matrix multiplication A times B $\endgroup$ – imranfat Jun 6 '13 at 14:49
  • $\begingroup$ I don't think using multiplication operator is necessary. You can write the product of matrices altogether without the operation. For instance, $\begin{bmatrix}1 & 0 \\ 0 & 1 \end{bmatrix} \begin{bmatrix}1 & 0 \\ 0 & 1 \end{bmatrix}$ $\endgroup$ – NasuSama Jun 6 '13 at 14:53
  • $\begingroup$ It is usually implicit. $\endgroup$ – copper.hat Jun 6 '13 at 14:54
  • $\begingroup$ I'm asking the well known symbol(not just nothing), but looks like there is no such symbol. Maybe, I can just define the operator. $\endgroup$ – user81234 Jun 6 '13 at 14:57
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    $\begingroup$ I wonder why there is no such symbol. Matrix multiplication is quite unusual for beginner and also it doesn't satisfy commutative law. $\endgroup$ – user81234 Jun 6 '13 at 15:04

Juxtaposition is the standard notational convention (to "write side by side") without an intermediary operation symbol): for matrices $A, B$ on which matrix multiplication is defined, write $AB$. Some texts may use the "dot" $A\cdot B$, but juxtaposition is more typical.

See the entry in Wikipedia: Matrix Multiplication to disambiguate "standard" matrix multiplication from other matrix products: Hadamard product $A\circ B$, Frobenius product $A:B$, and Kronecker product $A\otimes B$.

You'll see the "dot" and "cross" typically used with vectors (which are, also, matrices) to distinguish between the operations of the dot product and the cross product.


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