Prove that $operatorname{SL}(n,R)$ is connected.
$begingroup$
Prove that $operatorname{SL}(n, R)$ is connected.
The problem is I know only topological groups from Munkres only. Again Just started fundamental groups. So if anyone can explain to me how it is true in a lucid language and in an easy way such that it remains in my boundary of knowledge then it would be a great help. I have mentioned what I know.
Again if tag this in the wrong field. Please forgive me.
linear-algebra general-topology topological-groups
$endgroup$
add a comment |
$begingroup$
Prove that $operatorname{SL}(n, R)$ is connected.
The problem is I know only topological groups from Munkres only. Again Just started fundamental groups. So if anyone can explain to me how it is true in a lucid language and in an easy way such that it remains in my boundary of knowledge then it would be a great help. I have mentioned what I know.
Again if tag this in the wrong field. Please forgive me.
linear-algebra general-topology topological-groups
$endgroup$
2
$begingroup$
Since you asked, my opinion is that you don't need the algebraic topology tag.
$endgroup$
– Matt Samuel
Nov 7 '14 at 16:40
$begingroup$
On the other hand a linear-algebra tag would be very appropriate since, as the answer of @mookid shows, this is a consequence of basic facts in basic linear algebra.
$endgroup$
– Lee Mosher
Nov 7 '14 at 20:56
add a comment |
$begingroup$
Prove that $operatorname{SL}(n, R)$ is connected.
The problem is I know only topological groups from Munkres only. Again Just started fundamental groups. So if anyone can explain to me how it is true in a lucid language and in an easy way such that it remains in my boundary of knowledge then it would be a great help. I have mentioned what I know.
Again if tag this in the wrong field. Please forgive me.
linear-algebra general-topology topological-groups
$endgroup$
Prove that $operatorname{SL}(n, R)$ is connected.
The problem is I know only topological groups from Munkres only. Again Just started fundamental groups. So if anyone can explain to me how it is true in a lucid language and in an easy way such that it remains in my boundary of knowledge then it would be a great help. I have mentioned what I know.
Again if tag this in the wrong field. Please forgive me.
linear-algebra general-topology topological-groups
linear-algebra general-topology topological-groups
edited Jan 23 at 13:31
user549397
1,5081418
1,5081418
asked Nov 7 '14 at 16:38
user152715user152715
1
1
2
$begingroup$
Since you asked, my opinion is that you don't need the algebraic topology tag.
$endgroup$
– Matt Samuel
Nov 7 '14 at 16:40
$begingroup$
On the other hand a linear-algebra tag would be very appropriate since, as the answer of @mookid shows, this is a consequence of basic facts in basic linear algebra.
$endgroup$
– Lee Mosher
Nov 7 '14 at 20:56
add a comment |
2
$begingroup$
Since you asked, my opinion is that you don't need the algebraic topology tag.
$endgroup$
– Matt Samuel
Nov 7 '14 at 16:40
$begingroup$
On the other hand a linear-algebra tag would be very appropriate since, as the answer of @mookid shows, this is a consequence of basic facts in basic linear algebra.
$endgroup$
– Lee Mosher
Nov 7 '14 at 20:56
2
2
$begingroup$
Since you asked, my opinion is that you don't need the algebraic topology tag.
$endgroup$
– Matt Samuel
Nov 7 '14 at 16:40
$begingroup$
Since you asked, my opinion is that you don't need the algebraic topology tag.
$endgroup$
– Matt Samuel
Nov 7 '14 at 16:40
$begingroup$
On the other hand a linear-algebra tag would be very appropriate since, as the answer of @mookid shows, this is a consequence of basic facts in basic linear algebra.
$endgroup$
– Lee Mosher
Nov 7 '14 at 20:56
$begingroup$
On the other hand a linear-algebra tag would be very appropriate since, as the answer of @mookid shows, this is a consequence of basic facts in basic linear algebra.
$endgroup$
– Lee Mosher
Nov 7 '14 at 20:56
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
Hint: prove that if two matrices can be transformed one into another using row-echelon transformation, then they are connected.
as we focus on elements of $SL_n$, we only need to prove that transvections $L_i to l_i + aL_j$ connect elements.
let $Ain SL_n$, $B$ is the image of $A$ under the transvection $L_i to L_i + aL_j$.
Then
$$
gamma: [0,1]to SL_n
$$defined by
"$gamma(t)$ is the image of $A$ under the transvection $L_i to L_i + taL_j$
" is continuous, and such as $gamma(0) = A$, $gamma(1) = B$ (also, check that for every $t$, $gamma (t)in SL_n$). Hence $A,B$ are path connected.
$endgroup$
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
1
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
|
show 4 more comments
$begingroup$
Exercise 2.M.8(a) (Artin's Algebra, 2nd edition). The group $SL_n(mathbb{R})$ is generated by elementary matrices of the first type (see Exercise 2.4.8). Use this fact to prove that $SL_n(mathbb{R})$ is path-connected.
Let $sim$ be the binary operation corresponding to path-connectivity in $SL_n(mathbb{R})$; by my answer here, $sim$ is an equivalence relation.
In order to show $SL_n(mathbb{R})$ is path-connected, it suffices to show $Asim I_n$ for all $Ain SL_n(mathbb{R})$. But by my answer here, $A$ can be written as a (possibly empty) product of elementary matrices of the first type, so it in fact suffices to prove that$$E_{uv}(a)Msim M$$for all $Min SL_n(mathbb{R})$ and Type 1 elementary matrices $E_{uv}(a)$ ($1le u,,vle n$) of the form$$I_n + [a[(i,,j) = (u,,v)]]_{i,,j,=,1}^n.$$Yet$$Mto E_{uv}(b)M$$simply adds $b$ times row $j$ to row $i$, i.e. takes $r_i$ to $r_i+br_j$. For fixed $u$, $v$, $M$, this map is continuous in $b$ (and preserves the determinant), so the continuous function$$X(t) = E_{uv}(ta)M$$over $[0,1]$ takes$$X(0) = M to X(1) = E_{uv}(a)M$$while remaining inside $SL_n(mathbb{R})$, as desired.
$endgroup$
add a comment |
Your Answer
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2 Answers
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2 Answers
2
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$begingroup$
Hint: prove that if two matrices can be transformed one into another using row-echelon transformation, then they are connected.
as we focus on elements of $SL_n$, we only need to prove that transvections $L_i to l_i + aL_j$ connect elements.
let $Ain SL_n$, $B$ is the image of $A$ under the transvection $L_i to L_i + aL_j$.
Then
$$
gamma: [0,1]to SL_n
$$defined by
"$gamma(t)$ is the image of $A$ under the transvection $L_i to L_i + taL_j$
" is continuous, and such as $gamma(0) = A$, $gamma(1) = B$ (also, check that for every $t$, $gamma (t)in SL_n$). Hence $A,B$ are path connected.
$endgroup$
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
1
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
|
show 4 more comments
$begingroup$
Hint: prove that if two matrices can be transformed one into another using row-echelon transformation, then they are connected.
as we focus on elements of $SL_n$, we only need to prove that transvections $L_i to l_i + aL_j$ connect elements.
let $Ain SL_n$, $B$ is the image of $A$ under the transvection $L_i to L_i + aL_j$.
Then
$$
gamma: [0,1]to SL_n
$$defined by
"$gamma(t)$ is the image of $A$ under the transvection $L_i to L_i + taL_j$
" is continuous, and such as $gamma(0) = A$, $gamma(1) = B$ (also, check that for every $t$, $gamma (t)in SL_n$). Hence $A,B$ are path connected.
$endgroup$
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
1
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
|
show 4 more comments
$begingroup$
Hint: prove that if two matrices can be transformed one into another using row-echelon transformation, then they are connected.
as we focus on elements of $SL_n$, we only need to prove that transvections $L_i to l_i + aL_j$ connect elements.
let $Ain SL_n$, $B$ is the image of $A$ under the transvection $L_i to L_i + aL_j$.
Then
$$
gamma: [0,1]to SL_n
$$defined by
"$gamma(t)$ is the image of $A$ under the transvection $L_i to L_i + taL_j$
" is continuous, and such as $gamma(0) = A$, $gamma(1) = B$ (also, check that for every $t$, $gamma (t)in SL_n$). Hence $A,B$ are path connected.
$endgroup$
Hint: prove that if two matrices can be transformed one into another using row-echelon transformation, then they are connected.
as we focus on elements of $SL_n$, we only need to prove that transvections $L_i to l_i + aL_j$ connect elements.
let $Ain SL_n$, $B$ is the image of $A$ under the transvection $L_i to L_i + aL_j$.
Then
$$
gamma: [0,1]to SL_n
$$defined by
"$gamma(t)$ is the image of $A$ under the transvection $L_i to L_i + taL_j$
" is continuous, and such as $gamma(0) = A$, $gamma(1) = B$ (also, check that for every $t$, $gamma (t)in SL_n$). Hence $A,B$ are path connected.
edited Apr 30 '17 at 3:32


tommy xu3
9791621
9791621
answered Nov 7 '14 at 16:40
mookidmookid
25.6k52547
25.6k52547
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
1
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
|
show 4 more comments
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
1
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
$begingroup$
How do I do that? Using topological group definition?
$endgroup$
– user152715
Nov 7 '14 at 16:48
1
1
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
the transformations have explicit forms. Use the 'path-connected implies connected' implication.
$endgroup$
– mookid
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
can you please write this answer ilaborately then atleast I get an idea for this kind of questions.
$endgroup$
– user152715
Nov 7 '14 at 16:49
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
Because I am new to deal with these questions. Thats why I am requesting you. Please it will be a great help.
$endgroup$
– user152715
Nov 7 '14 at 16:52
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
$begingroup$
@user152715 I wrote the hint part. Now it is your turn to finish the proof. Tell me if you have other issues.
$endgroup$
– mookid
Nov 7 '14 at 16:55
|
show 4 more comments
$begingroup$
Exercise 2.M.8(a) (Artin's Algebra, 2nd edition). The group $SL_n(mathbb{R})$ is generated by elementary matrices of the first type (see Exercise 2.4.8). Use this fact to prove that $SL_n(mathbb{R})$ is path-connected.
Let $sim$ be the binary operation corresponding to path-connectivity in $SL_n(mathbb{R})$; by my answer here, $sim$ is an equivalence relation.
In order to show $SL_n(mathbb{R})$ is path-connected, it suffices to show $Asim I_n$ for all $Ain SL_n(mathbb{R})$. But by my answer here, $A$ can be written as a (possibly empty) product of elementary matrices of the first type, so it in fact suffices to prove that$$E_{uv}(a)Msim M$$for all $Min SL_n(mathbb{R})$ and Type 1 elementary matrices $E_{uv}(a)$ ($1le u,,vle n$) of the form$$I_n + [a[(i,,j) = (u,,v)]]_{i,,j,=,1}^n.$$Yet$$Mto E_{uv}(b)M$$simply adds $b$ times row $j$ to row $i$, i.e. takes $r_i$ to $r_i+br_j$. For fixed $u$, $v$, $M$, this map is continuous in $b$ (and preserves the determinant), so the continuous function$$X(t) = E_{uv}(ta)M$$over $[0,1]$ takes$$X(0) = M to X(1) = E_{uv}(a)M$$while remaining inside $SL_n(mathbb{R})$, as desired.
$endgroup$
add a comment |
$begingroup$
Exercise 2.M.8(a) (Artin's Algebra, 2nd edition). The group $SL_n(mathbb{R})$ is generated by elementary matrices of the first type (see Exercise 2.4.8). Use this fact to prove that $SL_n(mathbb{R})$ is path-connected.
Let $sim$ be the binary operation corresponding to path-connectivity in $SL_n(mathbb{R})$; by my answer here, $sim$ is an equivalence relation.
In order to show $SL_n(mathbb{R})$ is path-connected, it suffices to show $Asim I_n$ for all $Ain SL_n(mathbb{R})$. But by my answer here, $A$ can be written as a (possibly empty) product of elementary matrices of the first type, so it in fact suffices to prove that$$E_{uv}(a)Msim M$$for all $Min SL_n(mathbb{R})$ and Type 1 elementary matrices $E_{uv}(a)$ ($1le u,,vle n$) of the form$$I_n + [a[(i,,j) = (u,,v)]]_{i,,j,=,1}^n.$$Yet$$Mto E_{uv}(b)M$$simply adds $b$ times row $j$ to row $i$, i.e. takes $r_i$ to $r_i+br_j$. For fixed $u$, $v$, $M$, this map is continuous in $b$ (and preserves the determinant), so the continuous function$$X(t) = E_{uv}(ta)M$$over $[0,1]$ takes$$X(0) = M to X(1) = E_{uv}(a)M$$while remaining inside $SL_n(mathbb{R})$, as desired.
$endgroup$
add a comment |
$begingroup$
Exercise 2.M.8(a) (Artin's Algebra, 2nd edition). The group $SL_n(mathbb{R})$ is generated by elementary matrices of the first type (see Exercise 2.4.8). Use this fact to prove that $SL_n(mathbb{R})$ is path-connected.
Let $sim$ be the binary operation corresponding to path-connectivity in $SL_n(mathbb{R})$; by my answer here, $sim$ is an equivalence relation.
In order to show $SL_n(mathbb{R})$ is path-connected, it suffices to show $Asim I_n$ for all $Ain SL_n(mathbb{R})$. But by my answer here, $A$ can be written as a (possibly empty) product of elementary matrices of the first type, so it in fact suffices to prove that$$E_{uv}(a)Msim M$$for all $Min SL_n(mathbb{R})$ and Type 1 elementary matrices $E_{uv}(a)$ ($1le u,,vle n$) of the form$$I_n + [a[(i,,j) = (u,,v)]]_{i,,j,=,1}^n.$$Yet$$Mto E_{uv}(b)M$$simply adds $b$ times row $j$ to row $i$, i.e. takes $r_i$ to $r_i+br_j$. For fixed $u$, $v$, $M$, this map is continuous in $b$ (and preserves the determinant), so the continuous function$$X(t) = E_{uv}(ta)M$$over $[0,1]$ takes$$X(0) = M to X(1) = E_{uv}(a)M$$while remaining inside $SL_n(mathbb{R})$, as desired.
$endgroup$
Exercise 2.M.8(a) (Artin's Algebra, 2nd edition). The group $SL_n(mathbb{R})$ is generated by elementary matrices of the first type (see Exercise 2.4.8). Use this fact to prove that $SL_n(mathbb{R})$ is path-connected.
Let $sim$ be the binary operation corresponding to path-connectivity in $SL_n(mathbb{R})$; by my answer here, $sim$ is an equivalence relation.
In order to show $SL_n(mathbb{R})$ is path-connected, it suffices to show $Asim I_n$ for all $Ain SL_n(mathbb{R})$. But by my answer here, $A$ can be written as a (possibly empty) product of elementary matrices of the first type, so it in fact suffices to prove that$$E_{uv}(a)Msim M$$for all $Min SL_n(mathbb{R})$ and Type 1 elementary matrices $E_{uv}(a)$ ($1le u,,vle n$) of the form$$I_n + [a[(i,,j) = (u,,v)]]_{i,,j,=,1}^n.$$Yet$$Mto E_{uv}(b)M$$simply adds $b$ times row $j$ to row $i$, i.e. takes $r_i$ to $r_i+br_j$. For fixed $u$, $v$, $M$, this map is continuous in $b$ (and preserves the determinant), so the continuous function$$X(t) = E_{uv}(ta)M$$over $[0,1]$ takes$$X(0) = M to X(1) = E_{uv}(a)M$$while remaining inside $SL_n(mathbb{R})$, as desired.
edited Apr 13 '17 at 12:19
Community♦
1
1
answered Sep 24 '15 at 15:57
user203482
add a comment |
add a comment |
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2
$begingroup$
Since you asked, my opinion is that you don't need the algebraic topology tag.
$endgroup$
– Matt Samuel
Nov 7 '14 at 16:40
$begingroup$
On the other hand a linear-algebra tag would be very appropriate since, as the answer of @mookid shows, this is a consequence of basic facts in basic linear algebra.
$endgroup$
– Lee Mosher
Nov 7 '14 at 20:56