In Hilbert space $ dim(operatorname{coker}(T))=dim(ker(T^{*}))$
$begingroup$
$H$ is a Hilbert space, and $Tin B(H)$ continuous and Fredholm operator.
Same books in definition of Fredholm use (when work in Banach space)
$operatorname{ind}(T)=dim(ker(T))-dim(operatorname{coker}(T))$
and another's (when work with Hilbert space)
$operatorname{ind}(T)=dim(ker(T))-dim(ker(T^{*}))$ , $T^{*}$ is the adjoint operator
so how can i show that
$dim(operatorname{coker}(T))=dim(ker(T^{*}))$
$operatorname{coker}(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
thanks
operator-theory
$endgroup$
add a comment |
$begingroup$
$H$ is a Hilbert space, and $Tin B(H)$ continuous and Fredholm operator.
Same books in definition of Fredholm use (when work in Banach space)
$operatorname{ind}(T)=dim(ker(T))-dim(operatorname{coker}(T))$
and another's (when work with Hilbert space)
$operatorname{ind}(T)=dim(ker(T))-dim(ker(T^{*}))$ , $T^{*}$ is the adjoint operator
so how can i show that
$dim(operatorname{coker}(T))=dim(ker(T^{*}))$
$operatorname{coker}(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
thanks
operator-theory
$endgroup$
$begingroup$
you are allowed to substract the two equalities as long as all the terms are finite. I do not see the problem?
$endgroup$
– Picaud Vincent
Nov 30 '18 at 23:16
$begingroup$
@PicaudVincent my problem in my mind, is see the two definitions are the same, so well if we assume $T$ is Fredholm , see the boths dimensions are equal
$endgroup$
– user89940
Nov 30 '18 at 23:18
$begingroup$
$coker(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
$endgroup$
– user89940
Dec 1 '18 at 0:00
add a comment |
$begingroup$
$H$ is a Hilbert space, and $Tin B(H)$ continuous and Fredholm operator.
Same books in definition of Fredholm use (when work in Banach space)
$operatorname{ind}(T)=dim(ker(T))-dim(operatorname{coker}(T))$
and another's (when work with Hilbert space)
$operatorname{ind}(T)=dim(ker(T))-dim(ker(T^{*}))$ , $T^{*}$ is the adjoint operator
so how can i show that
$dim(operatorname{coker}(T))=dim(ker(T^{*}))$
$operatorname{coker}(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
thanks
operator-theory
$endgroup$
$H$ is a Hilbert space, and $Tin B(H)$ continuous and Fredholm operator.
Same books in definition of Fredholm use (when work in Banach space)
$operatorname{ind}(T)=dim(ker(T))-dim(operatorname{coker}(T))$
and another's (when work with Hilbert space)
$operatorname{ind}(T)=dim(ker(T))-dim(ker(T^{*}))$ , $T^{*}$ is the adjoint operator
so how can i show that
$dim(operatorname{coker}(T))=dim(ker(T^{*}))$
$operatorname{coker}(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
thanks
operator-theory
operator-theory
edited Dec 1 '18 at 0:12
user89940
asked Nov 30 '18 at 22:03
user89940user89940
797
797
$begingroup$
you are allowed to substract the two equalities as long as all the terms are finite. I do not see the problem?
$endgroup$
– Picaud Vincent
Nov 30 '18 at 23:16
$begingroup$
@PicaudVincent my problem in my mind, is see the two definitions are the same, so well if we assume $T$ is Fredholm , see the boths dimensions are equal
$endgroup$
– user89940
Nov 30 '18 at 23:18
$begingroup$
$coker(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
$endgroup$
– user89940
Dec 1 '18 at 0:00
add a comment |
$begingroup$
you are allowed to substract the two equalities as long as all the terms are finite. I do not see the problem?
$endgroup$
– Picaud Vincent
Nov 30 '18 at 23:16
$begingroup$
@PicaudVincent my problem in my mind, is see the two definitions are the same, so well if we assume $T$ is Fredholm , see the boths dimensions are equal
$endgroup$
– user89940
Nov 30 '18 at 23:18
$begingroup$
$coker(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
$endgroup$
– user89940
Dec 1 '18 at 0:00
$begingroup$
you are allowed to substract the two equalities as long as all the terms are finite. I do not see the problem?
$endgroup$
– Picaud Vincent
Nov 30 '18 at 23:16
$begingroup$
you are allowed to substract the two equalities as long as all the terms are finite. I do not see the problem?
$endgroup$
– Picaud Vincent
Nov 30 '18 at 23:16
$begingroup$
@PicaudVincent my problem in my mind, is see the two definitions are the same, so well if we assume $T$ is Fredholm , see the boths dimensions are equal
$endgroup$
– user89940
Nov 30 '18 at 23:18
$begingroup$
@PicaudVincent my problem in my mind, is see the two definitions are the same, so well if we assume $T$ is Fredholm , see the boths dimensions are equal
$endgroup$
– user89940
Nov 30 '18 at 23:18
$begingroup$
$coker(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
$endgroup$
– user89940
Dec 1 '18 at 0:00
$begingroup$
$coker(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
$endgroup$
– user89940
Dec 1 '18 at 0:00
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
For any closed subspace $K$ of a Hilbert space $H$, we have
$$H/Kcong K^perp.$$
Proof.
$newcommand{co}{operatorname{coker}}$Let begin{align*}Phi: & K^perpto H/K\
& hmapsto [h]end{align*}
(1) Of course, $Phi$ is linear bounded.
(2) $Phi$ is injective. Suppose $hin K^perp$ such that $Phi(h)=0$, then $hin K^perpcap K$, so $h=0$.
(3) $Phi$ is surjective. For any $hin H$, there is some $h'in K^perp$ such that $h-h'in K$, thus $Phi(h')=[h']=[h]$.
Noting that $TH$ is closed subspace in the question, $H/THcong (TH)^perp$.
$endgroup$
1
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
1
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
|
show 4 more comments
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3020704%2fin-hilbert-space-dim-operatornamecokert-dim-kert%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
For any closed subspace $K$ of a Hilbert space $H$, we have
$$H/Kcong K^perp.$$
Proof.
$newcommand{co}{operatorname{coker}}$Let begin{align*}Phi: & K^perpto H/K\
& hmapsto [h]end{align*}
(1) Of course, $Phi$ is linear bounded.
(2) $Phi$ is injective. Suppose $hin K^perp$ such that $Phi(h)=0$, then $hin K^perpcap K$, so $h=0$.
(3) $Phi$ is surjective. For any $hin H$, there is some $h'in K^perp$ such that $h-h'in K$, thus $Phi(h')=[h']=[h]$.
Noting that $TH$ is closed subspace in the question, $H/THcong (TH)^perp$.
$endgroup$
1
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
1
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
|
show 4 more comments
$begingroup$
For any closed subspace $K$ of a Hilbert space $H$, we have
$$H/Kcong K^perp.$$
Proof.
$newcommand{co}{operatorname{coker}}$Let begin{align*}Phi: & K^perpto H/K\
& hmapsto [h]end{align*}
(1) Of course, $Phi$ is linear bounded.
(2) $Phi$ is injective. Suppose $hin K^perp$ such that $Phi(h)=0$, then $hin K^perpcap K$, so $h=0$.
(3) $Phi$ is surjective. For any $hin H$, there is some $h'in K^perp$ such that $h-h'in K$, thus $Phi(h')=[h']=[h]$.
Noting that $TH$ is closed subspace in the question, $H/THcong (TH)^perp$.
$endgroup$
1
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
1
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
|
show 4 more comments
$begingroup$
For any closed subspace $K$ of a Hilbert space $H$, we have
$$H/Kcong K^perp.$$
Proof.
$newcommand{co}{operatorname{coker}}$Let begin{align*}Phi: & K^perpto H/K\
& hmapsto [h]end{align*}
(1) Of course, $Phi$ is linear bounded.
(2) $Phi$ is injective. Suppose $hin K^perp$ such that $Phi(h)=0$, then $hin K^perpcap K$, so $h=0$.
(3) $Phi$ is surjective. For any $hin H$, there is some $h'in K^perp$ such that $h-h'in K$, thus $Phi(h')=[h']=[h]$.
Noting that $TH$ is closed subspace in the question, $H/THcong (TH)^perp$.
$endgroup$
For any closed subspace $K$ of a Hilbert space $H$, we have
$$H/Kcong K^perp.$$
Proof.
$newcommand{co}{operatorname{coker}}$Let begin{align*}Phi: & K^perpto H/K\
& hmapsto [h]end{align*}
(1) Of course, $Phi$ is linear bounded.
(2) $Phi$ is injective. Suppose $hin K^perp$ such that $Phi(h)=0$, then $hin K^perpcap K$, so $h=0$.
(3) $Phi$ is surjective. For any $hin H$, there is some $h'in K^perp$ such that $h-h'in K$, thus $Phi(h')=[h']=[h]$.
Noting that $TH$ is closed subspace in the question, $H/THcong (TH)^perp$.
edited Dec 1 '18 at 4:22
answered Dec 1 '18 at 2:31
C.DingC.Ding
1,3911321
1,3911321
1
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
1
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
|
show 4 more comments
1
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
1
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
1
1
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
thanks, so hypothesis of $T$ fredholm is needed for asume $T(X)$ is closed
$endgroup$
– user89940
Dec 1 '18 at 3:10
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
For any subset $S$ of $H$, $H/overline{span{S}}=S^perp$. The very usage of $T(H)$ is closed is $T(H)=overline{span{T(H)}}$
$endgroup$
– C.Ding
Dec 1 '18 at 4:13
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
A better answer has been updated.
$endgroup$
– C.Ding
Dec 1 '18 at 4:23
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
$begingroup$
the hypothesis of $T(H)$ closed is needed for definition in Hilbert version right? because in Banach version $T$ operator with finite coker have image closed. But in hilbert version say "finite dimension of $Ker(T)$ and $Ker(T^{*})$" not impliy $T(H)$ closed? like this answer math.stackexchange.com/questions/1107449/…
$endgroup$
– user89940
Dec 1 '18 at 16:15
1
1
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
$begingroup$
Yes. If you define coker of an operator $u:Xto Y$ between Banach spaces as $ker u^#$, you will also need the closedness of $uX$ in the definition of a Fredholm operator. If you define the coker of $u$ as a linear space $Y/uX$, then you need not the closedness of uX in any version.
$endgroup$
– C.Ding
Dec 5 '18 at 7:53
|
show 4 more comments
Thanks for contributing an answer to Mathematics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3020704%2fin-hilbert-space-dim-operatornamecokert-dim-kert%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
$begingroup$
you are allowed to substract the two equalities as long as all the terms are finite. I do not see the problem?
$endgroup$
– Picaud Vincent
Nov 30 '18 at 23:16
$begingroup$
@PicaudVincent my problem in my mind, is see the two definitions are the same, so well if we assume $T$ is Fredholm , see the boths dimensions are equal
$endgroup$
– user89940
Nov 30 '18 at 23:18
$begingroup$
$coker(T)=H/T(H)$ and $Ker(T^{*})=(T(H))^{perp}$. so in Hilbert is true $H/T(H)approx (T(H))^{perp}$ ?
$endgroup$
– user89940
Dec 1 '18 at 0:00