if $A in C^{2015,2015}$ and $rank(A) 15$
$begingroup$
I want to solve that thesis:
if $A in C^{2015,2015}$ and $rank(A) < 1000$ proof that $dim(ker(A+A^T)) > 15 $
from the fact that $$dim(im(A)) = dim(im(A^T))$$ and
$$ dim(ker(A))+dim(im(A))=n $$
it follows that
$$dim(ker(A)) = dim(ker(A^T))$$
We know that $rank(A) < 1000$. Hence $dim(ker(A))>1015$
But there I have stuck...
thanks for your time
linear-algebra matrices matrix-rank
$endgroup$
add a comment |
$begingroup$
I want to solve that thesis:
if $A in C^{2015,2015}$ and $rank(A) < 1000$ proof that $dim(ker(A+A^T)) > 15 $
from the fact that $$dim(im(A)) = dim(im(A^T))$$ and
$$ dim(ker(A))+dim(im(A))=n $$
it follows that
$$dim(ker(A)) = dim(ker(A^T))$$
We know that $rank(A) < 1000$. Hence $dim(ker(A))>1015$
But there I have stuck...
thanks for your time
linear-algebra matrices matrix-rank
$endgroup$
add a comment |
$begingroup$
I want to solve that thesis:
if $A in C^{2015,2015}$ and $rank(A) < 1000$ proof that $dim(ker(A+A^T)) > 15 $
from the fact that $$dim(im(A)) = dim(im(A^T))$$ and
$$ dim(ker(A))+dim(im(A))=n $$
it follows that
$$dim(ker(A)) = dim(ker(A^T))$$
We know that $rank(A) < 1000$. Hence $dim(ker(A))>1015$
But there I have stuck...
thanks for your time
linear-algebra matrices matrix-rank
$endgroup$
I want to solve that thesis:
if $A in C^{2015,2015}$ and $rank(A) < 1000$ proof that $dim(ker(A+A^T)) > 15 $
from the fact that $$dim(im(A)) = dim(im(A^T))$$ and
$$ dim(ker(A))+dim(im(A))=n $$
it follows that
$$dim(ker(A)) = dim(ker(A^T))$$
We know that $rank(A) < 1000$. Hence $dim(ker(A))>1015$
But there I have stuck...
thanks for your time
linear-algebra matrices matrix-rank
linear-algebra matrices matrix-rank
edited Dec 30 '18 at 15:20
Yanko
8,6922830
8,6922830
asked Dec 30 '18 at 15:18
VirtualUserVirtualUser
1,329317
1,329317
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
You're one line from the solution:
You showed that $dim (ker A) > 1015$ (so $A$ sends a vector space of dimension $1015$ to zero).
Moreover since $dim (Im A ) = dim (Im A^T)$ you also have that the dimensions of the kernels equal and so $dim(ker A^T)>1015$.
Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$). This completes the proof, because $ker (A+A^T)$ contains $ker Acap ker A^T$.
$endgroup$
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
add a comment |
$begingroup$
Hint: $operatorname{dim}(operatorname {im}(A+A^t)=operatorname{dim}(operatorname{im}A)+operatorname{dim}(operatorname{im}A^t)-operatorname{dim}(operatorname{im}Acapoperatorname{im}A^t)lt2000$.
$endgroup$
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
add a comment |
Your Answer
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2 Answers
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active
oldest
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2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
You're one line from the solution:
You showed that $dim (ker A) > 1015$ (so $A$ sends a vector space of dimension $1015$ to zero).
Moreover since $dim (Im A ) = dim (Im A^T)$ you also have that the dimensions of the kernels equal and so $dim(ker A^T)>1015$.
Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$). This completes the proof, because $ker (A+A^T)$ contains $ker Acap ker A^T$.
$endgroup$
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
add a comment |
$begingroup$
You're one line from the solution:
You showed that $dim (ker A) > 1015$ (so $A$ sends a vector space of dimension $1015$ to zero).
Moreover since $dim (Im A ) = dim (Im A^T)$ you also have that the dimensions of the kernels equal and so $dim(ker A^T)>1015$.
Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$). This completes the proof, because $ker (A+A^T)$ contains $ker Acap ker A^T$.
$endgroup$
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
add a comment |
$begingroup$
You're one line from the solution:
You showed that $dim (ker A) > 1015$ (so $A$ sends a vector space of dimension $1015$ to zero).
Moreover since $dim (Im A ) = dim (Im A^T)$ you also have that the dimensions of the kernels equal and so $dim(ker A^T)>1015$.
Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$). This completes the proof, because $ker (A+A^T)$ contains $ker Acap ker A^T$.
$endgroup$
You're one line from the solution:
You showed that $dim (ker A) > 1015$ (so $A$ sends a vector space of dimension $1015$ to zero).
Moreover since $dim (Im A ) = dim (Im A^T)$ you also have that the dimensions of the kernels equal and so $dim(ker A^T)>1015$.
Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$). This completes the proof, because $ker (A+A^T)$ contains $ker Acap ker A^T$.
answered Dec 30 '18 at 15:23
YankoYanko
8,6922830
8,6922830
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
add a comment |
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
Sorry if it is stupid question but I am sitting and I have no idea why $ dim(ker A + ker A^T)leq 2015$. Could I ask you for an explanation?
$endgroup$
– VirtualUser
Dec 30 '18 at 15:45
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
@VirtualUser Both $ker A$ and $ker A^T$ are subspaces of $mathbb{C}^{2015}$. Therefore so is their sum.
$endgroup$
– Yanko
Dec 30 '18 at 15:47
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
"Therefore by the dimensions theorem we have that the dimension of $ker A cap ker A^T$ is at least $15$ (because $dim(ker A + ker A^T)leq 2015$)." Ok but how from dimensions theorem I get this proposal? Dimension theorem says that $dim(im(T)) + dim(kernel(T)) = n $, but there, If we assume that T is $ ker A + ker A^T$ I haven't got neither dim(im(T)) nor dim(kernel(T))
$endgroup$
– VirtualUser
Dec 30 '18 at 16:04
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
@VirtualUser This is the other dimension theorem. I'm talking about this $dim (U+W) = dim U + dim W - dim Ucap W$. Insert $U=ker A$ and $W=ker A^T$.
$endgroup$
– Yanko
Dec 30 '18 at 16:05
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
$begingroup$
Aaah, now I understand, you deserve a lot of thanks!
$endgroup$
– VirtualUser
Dec 30 '18 at 16:07
add a comment |
$begingroup$
Hint: $operatorname{dim}(operatorname {im}(A+A^t)=operatorname{dim}(operatorname{im}A)+operatorname{dim}(operatorname{im}A^t)-operatorname{dim}(operatorname{im}Acapoperatorname{im}A^t)lt2000$.
$endgroup$
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
add a comment |
$begingroup$
Hint: $operatorname{dim}(operatorname {im}(A+A^t)=operatorname{dim}(operatorname{im}A)+operatorname{dim}(operatorname{im}A^t)-operatorname{dim}(operatorname{im}Acapoperatorname{im}A^t)lt2000$.
$endgroup$
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
add a comment |
$begingroup$
Hint: $operatorname{dim}(operatorname {im}(A+A^t)=operatorname{dim}(operatorname{im}A)+operatorname{dim}(operatorname{im}A^t)-operatorname{dim}(operatorname{im}Acapoperatorname{im}A^t)lt2000$.
$endgroup$
Hint: $operatorname{dim}(operatorname {im}(A+A^t)=operatorname{dim}(operatorname{im}A)+operatorname{dim}(operatorname{im}A^t)-operatorname{dim}(operatorname{im}Acapoperatorname{im}A^t)lt2000$.
answered Dec 30 '18 at 15:34
Chris CusterChris Custer
14.5k3827
14.5k3827
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
add a comment |
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
$begingroup$
No, using the hypothesis, less than $1000+1000=2000$.
$endgroup$
– Chris Custer
Dec 30 '18 at 15:43
add a comment |
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