Ideal of matrix ring
I'm going over some exercises and I'm not quite sure if I completely understand this one.
Let $R=M_3(mathbb{Q})$, i.e. $R$ is the ring of all $3times3$ matrices over rational numbers. Describe the minimal right ideal of $R$ containing the matrix
$$begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}$$
M̶y̶ ̶g̶u̶e̶s̶s̶ ̶w̶a̶s̶ ̶t̶h̶a̶t̶ ̶I̶'̶m̶ ̶j̶u̶s̶t̶ ̶s̶u̶p̶p̶o̶s̶e̶d̶ ̶t̶o̶ ̶f̶i̶n̶d̶ ̶a̶ ̶m̶a̶t̶r̶i̶x̶ ̶i̶ ̶t̶h̶a̶t̶ ̶f̶i̶t̶s̶ ̶t̶h̶e̶ ̶d̶e̶f̶i̶n̶i̶t̶i̶o̶n̶ ̶o̶f̶ ̶a̶ ̶r̶i̶g̶h̶t̶ ̶i̶d̶e̶a̶l̶,̶ ̶w̶h̶i̶c̶h̶ ̶i̶s̶ ̶∀̶ ̶r̶ ̶∈̶ ̶R̶:̶ ̶i̶ ̶·̶ ̶r̶ ̶∈̶ ̶I̶ ̶(̶r̶ ̶b̶e̶i̶n̶g̶ ̶t̶h̶e̶ ̶g̶i̶v̶e̶n̶ ̶m̶a̶t̶r̶i̶x̶)̶ ̶a̶n̶d̶ ̶I̶ ̶=̶ ̶{̶(̶i̶)̶}̶ ̶.̶
But the more I tried to find something similar to this problem, the more I think that this is absolutely wrong. Can somebody help me with this and maybe explain how to get to the solution?
Thank you!
EDIT
My previous idea was a mix up of definitions, from the comments I now understand that I need to find $I$ (which contains the given matrix), but I'm still confused as to how to do so.
abstract-algebra matrices ring-theory ideals
New contributor
add a comment |
I'm going over some exercises and I'm not quite sure if I completely understand this one.
Let $R=M_3(mathbb{Q})$, i.e. $R$ is the ring of all $3times3$ matrices over rational numbers. Describe the minimal right ideal of $R$ containing the matrix
$$begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}$$
M̶y̶ ̶g̶u̶e̶s̶s̶ ̶w̶a̶s̶ ̶t̶h̶a̶t̶ ̶I̶'̶m̶ ̶j̶u̶s̶t̶ ̶s̶u̶p̶p̶o̶s̶e̶d̶ ̶t̶o̶ ̶f̶i̶n̶d̶ ̶a̶ ̶m̶a̶t̶r̶i̶x̶ ̶i̶ ̶t̶h̶a̶t̶ ̶f̶i̶t̶s̶ ̶t̶h̶e̶ ̶d̶e̶f̶i̶n̶i̶t̶i̶o̶n̶ ̶o̶f̶ ̶a̶ ̶r̶i̶g̶h̶t̶ ̶i̶d̶e̶a̶l̶,̶ ̶w̶h̶i̶c̶h̶ ̶i̶s̶ ̶∀̶ ̶r̶ ̶∈̶ ̶R̶:̶ ̶i̶ ̶·̶ ̶r̶ ̶∈̶ ̶I̶ ̶(̶r̶ ̶b̶e̶i̶n̶g̶ ̶t̶h̶e̶ ̶g̶i̶v̶e̶n̶ ̶m̶a̶t̶r̶i̶x̶)̶ ̶a̶n̶d̶ ̶I̶ ̶=̶ ̶{̶(̶i̶)̶}̶ ̶.̶
But the more I tried to find something similar to this problem, the more I think that this is absolutely wrong. Can somebody help me with this and maybe explain how to get to the solution?
Thank you!
EDIT
My previous idea was a mix up of definitions, from the comments I now understand that I need to find $I$ (which contains the given matrix), but I'm still confused as to how to do so.
abstract-algebra matrices ring-theory ideals
New contributor
3
Ideals are not matrices! Ideals are sets of matrices. You need to find the smallest $I subseteq R$ such that $left(array{1&0&1\1&1&0\0&1&1}right)in I$ and for any $r in R$ and any $i in I$, $ir in I$.
– user3482749
Jan 4 at 21:26
I second what @user3482749 said. It seems that you don't quite understand the definition of ideals, so you need to go back and read it more carefully. What you stated as a "definition" has bits and pieces of the correct one, but the way it's stated doesn't make much sense...
– zipirovich
Jan 4 at 22:25
add a comment |
I'm going over some exercises and I'm not quite sure if I completely understand this one.
Let $R=M_3(mathbb{Q})$, i.e. $R$ is the ring of all $3times3$ matrices over rational numbers. Describe the minimal right ideal of $R$ containing the matrix
$$begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}$$
M̶y̶ ̶g̶u̶e̶s̶s̶ ̶w̶a̶s̶ ̶t̶h̶a̶t̶ ̶I̶'̶m̶ ̶j̶u̶s̶t̶ ̶s̶u̶p̶p̶o̶s̶e̶d̶ ̶t̶o̶ ̶f̶i̶n̶d̶ ̶a̶ ̶m̶a̶t̶r̶i̶x̶ ̶i̶ ̶t̶h̶a̶t̶ ̶f̶i̶t̶s̶ ̶t̶h̶e̶ ̶d̶e̶f̶i̶n̶i̶t̶i̶o̶n̶ ̶o̶f̶ ̶a̶ ̶r̶i̶g̶h̶t̶ ̶i̶d̶e̶a̶l̶,̶ ̶w̶h̶i̶c̶h̶ ̶i̶s̶ ̶∀̶ ̶r̶ ̶∈̶ ̶R̶:̶ ̶i̶ ̶·̶ ̶r̶ ̶∈̶ ̶I̶ ̶(̶r̶ ̶b̶e̶i̶n̶g̶ ̶t̶h̶e̶ ̶g̶i̶v̶e̶n̶ ̶m̶a̶t̶r̶i̶x̶)̶ ̶a̶n̶d̶ ̶I̶ ̶=̶ ̶{̶(̶i̶)̶}̶ ̶.̶
But the more I tried to find something similar to this problem, the more I think that this is absolutely wrong. Can somebody help me with this and maybe explain how to get to the solution?
Thank you!
EDIT
My previous idea was a mix up of definitions, from the comments I now understand that I need to find $I$ (which contains the given matrix), but I'm still confused as to how to do so.
abstract-algebra matrices ring-theory ideals
New contributor
I'm going over some exercises and I'm not quite sure if I completely understand this one.
Let $R=M_3(mathbb{Q})$, i.e. $R$ is the ring of all $3times3$ matrices over rational numbers. Describe the minimal right ideal of $R$ containing the matrix
$$begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}$$
M̶y̶ ̶g̶u̶e̶s̶s̶ ̶w̶a̶s̶ ̶t̶h̶a̶t̶ ̶I̶'̶m̶ ̶j̶u̶s̶t̶ ̶s̶u̶p̶p̶o̶s̶e̶d̶ ̶t̶o̶ ̶f̶i̶n̶d̶ ̶a̶ ̶m̶a̶t̶r̶i̶x̶ ̶i̶ ̶t̶h̶a̶t̶ ̶f̶i̶t̶s̶ ̶t̶h̶e̶ ̶d̶e̶f̶i̶n̶i̶t̶i̶o̶n̶ ̶o̶f̶ ̶a̶ ̶r̶i̶g̶h̶t̶ ̶i̶d̶e̶a̶l̶,̶ ̶w̶h̶i̶c̶h̶ ̶i̶s̶ ̶∀̶ ̶r̶ ̶∈̶ ̶R̶:̶ ̶i̶ ̶·̶ ̶r̶ ̶∈̶ ̶I̶ ̶(̶r̶ ̶b̶e̶i̶n̶g̶ ̶t̶h̶e̶ ̶g̶i̶v̶e̶n̶ ̶m̶a̶t̶r̶i̶x̶)̶ ̶a̶n̶d̶ ̶I̶ ̶=̶ ̶{̶(̶i̶)̶}̶ ̶.̶
But the more I tried to find something similar to this problem, the more I think that this is absolutely wrong. Can somebody help me with this and maybe explain how to get to the solution?
Thank you!
EDIT
My previous idea was a mix up of definitions, from the comments I now understand that I need to find $I$ (which contains the given matrix), but I'm still confused as to how to do so.
abstract-algebra matrices ring-theory ideals
abstract-algebra matrices ring-theory ideals
New contributor
New contributor
edited Jan 4 at 22:41
Alex
New contributor
asked Jan 4 at 21:20
AlexAlex
304
304
New contributor
New contributor
3
Ideals are not matrices! Ideals are sets of matrices. You need to find the smallest $I subseteq R$ such that $left(array{1&0&1\1&1&0\0&1&1}right)in I$ and for any $r in R$ and any $i in I$, $ir in I$.
– user3482749
Jan 4 at 21:26
I second what @user3482749 said. It seems that you don't quite understand the definition of ideals, so you need to go back and read it more carefully. What you stated as a "definition" has bits and pieces of the correct one, but the way it's stated doesn't make much sense...
– zipirovich
Jan 4 at 22:25
add a comment |
3
Ideals are not matrices! Ideals are sets of matrices. You need to find the smallest $I subseteq R$ such that $left(array{1&0&1\1&1&0\0&1&1}right)in I$ and for any $r in R$ and any $i in I$, $ir in I$.
– user3482749
Jan 4 at 21:26
I second what @user3482749 said. It seems that you don't quite understand the definition of ideals, so you need to go back and read it more carefully. What you stated as a "definition" has bits and pieces of the correct one, but the way it's stated doesn't make much sense...
– zipirovich
Jan 4 at 22:25
3
3
Ideals are not matrices! Ideals are sets of matrices. You need to find the smallest $I subseteq R$ such that $left(array{1&0&1\1&1&0\0&1&1}right)in I$ and for any $r in R$ and any $i in I$, $ir in I$.
– user3482749
Jan 4 at 21:26
Ideals are not matrices! Ideals are sets of matrices. You need to find the smallest $I subseteq R$ such that $left(array{1&0&1\1&1&0\0&1&1}right)in I$ and for any $r in R$ and any $i in I$, $ir in I$.
– user3482749
Jan 4 at 21:26
I second what @user3482749 said. It seems that you don't quite understand the definition of ideals, so you need to go back and read it more carefully. What you stated as a "definition" has bits and pieces of the correct one, but the way it's stated doesn't make much sense...
– zipirovich
Jan 4 at 22:25
I second what @user3482749 said. It seems that you don't quite understand the definition of ideals, so you need to go back and read it more carefully. What you stated as a "definition" has bits and pieces of the correct one, but the way it's stated doesn't make much sense...
– zipirovich
Jan 4 at 22:25
add a comment |
1 Answer
1
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oldest
votes
The minimal right ideal of $R$ containing $rin R$ is $rR={rs:sin R}$. In your case it is the set of all products of the form
$$
begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}
begin{bmatrix}
a_{11} & a_{12} & a_{13} \
a_{21} & a_{22} & a_{23} \
a_{31} & a_{32} & a_{33} \
end{bmatrix}
$$
where the second matrix varies through all elements of $R=M_{3}(mathbb{Q})$.
Can this be described more easily, at least in this case? Well, the given matrix is…
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
2
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
|
show 5 more comments
Your Answer
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The minimal right ideal of $R$ containing $rin R$ is $rR={rs:sin R}$. In your case it is the set of all products of the form
$$
begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}
begin{bmatrix}
a_{11} & a_{12} & a_{13} \
a_{21} & a_{22} & a_{23} \
a_{31} & a_{32} & a_{33} \
end{bmatrix}
$$
where the second matrix varies through all elements of $R=M_{3}(mathbb{Q})$.
Can this be described more easily, at least in this case? Well, the given matrix is…
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
2
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
|
show 5 more comments
The minimal right ideal of $R$ containing $rin R$ is $rR={rs:sin R}$. In your case it is the set of all products of the form
$$
begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}
begin{bmatrix}
a_{11} & a_{12} & a_{13} \
a_{21} & a_{22} & a_{23} \
a_{31} & a_{32} & a_{33} \
end{bmatrix}
$$
where the second matrix varies through all elements of $R=M_{3}(mathbb{Q})$.
Can this be described more easily, at least in this case? Well, the given matrix is…
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
2
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
|
show 5 more comments
The minimal right ideal of $R$ containing $rin R$ is $rR={rs:sin R}$. In your case it is the set of all products of the form
$$
begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}
begin{bmatrix}
a_{11} & a_{12} & a_{13} \
a_{21} & a_{22} & a_{23} \
a_{31} & a_{32} & a_{33} \
end{bmatrix}
$$
where the second matrix varies through all elements of $R=M_{3}(mathbb{Q})$.
Can this be described more easily, at least in this case? Well, the given matrix is…
The minimal right ideal of $R$ containing $rin R$ is $rR={rs:sin R}$. In your case it is the set of all products of the form
$$
begin{bmatrix}
1 & 0 & 1 \
1 & 1 & 0 \
0 & 1 & 1 \
end{bmatrix}
begin{bmatrix}
a_{11} & a_{12} & a_{13} \
a_{21} & a_{22} & a_{23} \
a_{31} & a_{32} & a_{33} \
end{bmatrix}
$$
where the second matrix varies through all elements of $R=M_{3}(mathbb{Q})$.
Can this be described more easily, at least in this case? Well, the given matrix is…
edited Jan 4 at 23:15
answered Jan 4 at 22:50
egregegreg
179k1485202
179k1485202
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
2
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
|
show 5 more comments
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
2
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
that's it? just the product of those two matrices? I should've known it wasn't anything too complicated, thank you very much
– Alex
Jan 4 at 23:09
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
@Alex No, you didn't read carefully or I didn't explain myself too well: it is the set of all matrices of that form, infinitely many of them. But in this particular case, a property of the fixed matrix can be used.
– egreg
Jan 4 at 23:13
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
no, sorry I have no idea where you're going with this
– Alex
Jan 4 at 23:38
2
2
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
@Alex Call $r$ the given matrix. Then $r^{-1}$ exists and belongs to $R$, so among the elements of $rR$ there is $rr^{-1}=1$.
– egreg
Jan 4 at 23:50
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
okay so the ideal will contain identity??
– Alex
Jan 5 at 0:14
|
show 5 more comments
Alex is a new contributor. Be nice, and check out our Code of Conduct.
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3
Ideals are not matrices! Ideals are sets of matrices. You need to find the smallest $I subseteq R$ such that $left(array{1&0&1\1&1&0\0&1&1}right)in I$ and for any $r in R$ and any $i in I$, $ir in I$.
– user3482749
Jan 4 at 21:26
I second what @user3482749 said. It seems that you don't quite understand the definition of ideals, so you need to go back and read it more carefully. What you stated as a "definition" has bits and pieces of the correct one, but the way it's stated doesn't make much sense...
– zipirovich
Jan 4 at 22:25