- #1
cjellison
- 18
- 0
Consider the set of 2x2 matrices which form a ring under matrix multiplication and matrix addition.
[itex]\mathbb{R}^3[/itex] is module defined over this ring.
So, we have three dimensional vectors whose elements are 2x2 matrices.
My question: Can I also define another "scalar multiplication" that is over the field of real numbers (well, I know you can)...what is such a structure called? For example, I want it to do the following:
[tex]
3
\begin{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=
\begin{pmatrix}
3
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
3\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
3\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
3\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=
\begin{pmatrix}
\begin{pmatrix}
3a & 3b\\
3c & 3d
\end{pmatrix}
&
\begin{pmatrix}
3 & 3\\
3 & 3
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
3 & 6\\
12 & 9
\end{pmatrix}
\end{pmatrix}
[/tex]
in addition to:
[tex]
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=
\begin{pmatrix}
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=\begin{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
[/tex]
[itex]\mathbb{R}^3[/itex] is module defined over this ring.
So, we have three dimensional vectors whose elements are 2x2 matrices.
My question: Can I also define another "scalar multiplication" that is over the field of real numbers (well, I know you can)...what is such a structure called? For example, I want it to do the following:
[tex]
3
\begin{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=
\begin{pmatrix}
3
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
3\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
3\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
3\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=
\begin{pmatrix}
\begin{pmatrix}
3a & 3b\\
3c & 3d
\end{pmatrix}
&
\begin{pmatrix}
3 & 3\\
3 & 3
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
3 & 6\\
12 & 9
\end{pmatrix}
\end{pmatrix}
[/tex]
in addition to:
[tex]
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=
\begin{pmatrix}
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
=\begin{pmatrix}
\begin{pmatrix}
a & b\\
c & d
\end{pmatrix}
&
\begin{pmatrix}
1 & 1\\
1 & 1
\end{pmatrix}\\
\begin{pmatrix}
0 & 0\\
0 & 0
\end{pmatrix}
&
\begin{pmatrix}
1 & 2\\
4 & 3
\end{pmatrix}
\end{pmatrix}
[/tex]