Upper Triangular Matrix and Gram-Schmidt











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If $T$ is an operator on the finite dimensional vector space $V$ which has a basis $mathcal{B}$ for which the matrix representation of $T$ with this basis is upper-triangular, does it follow that $T$ represented with respect to the basis obtained from $mathcal{B}$ by Gram-Schmidt is also upper-triangular?










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  • Let $mathcal{C}$ be the basis obtained from $mathcal{B}$ by Gram-Schmidt. Is the change-of-basis matrix between $mathcal{B}$ and $mathcal{C}$ upper-triangular? (The answer depends somewhat on how exactly you define Gram-Schmidt.) If the answer is "yes", then the answer to your question is "yes" as well, because products and inverses of upper-triangular matrices are upper-triangular.
    – darij grinberg
    Nov 13 at 20:58










  • @darijgrinberg By Gram-Schmidt, I mean by procedure whereby one transforms a basis into an orthonormal basis. Is that what you had in mind, too?
    – user193319
    Nov 13 at 21:00










  • Yes, but there are several of these procedures. In your version, is the $j$-th vector of $mathcal{C}$ a linear combination of the first $j$ vectors of $mathcal{B}$ ? If so, the answer is "yes".
    – darij grinberg
    Nov 13 at 21:02















up vote
0
down vote

favorite












If $T$ is an operator on the finite dimensional vector space $V$ which has a basis $mathcal{B}$ for which the matrix representation of $T$ with this basis is upper-triangular, does it follow that $T$ represented with respect to the basis obtained from $mathcal{B}$ by Gram-Schmidt is also upper-triangular?










share|cite|improve this question






















  • Let $mathcal{C}$ be the basis obtained from $mathcal{B}$ by Gram-Schmidt. Is the change-of-basis matrix between $mathcal{B}$ and $mathcal{C}$ upper-triangular? (The answer depends somewhat on how exactly you define Gram-Schmidt.) If the answer is "yes", then the answer to your question is "yes" as well, because products and inverses of upper-triangular matrices are upper-triangular.
    – darij grinberg
    Nov 13 at 20:58










  • @darijgrinberg By Gram-Schmidt, I mean by procedure whereby one transforms a basis into an orthonormal basis. Is that what you had in mind, too?
    – user193319
    Nov 13 at 21:00










  • Yes, but there are several of these procedures. In your version, is the $j$-th vector of $mathcal{C}$ a linear combination of the first $j$ vectors of $mathcal{B}$ ? If so, the answer is "yes".
    – darij grinberg
    Nov 13 at 21:02













up vote
0
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favorite









up vote
0
down vote

favorite











If $T$ is an operator on the finite dimensional vector space $V$ which has a basis $mathcal{B}$ for which the matrix representation of $T$ with this basis is upper-triangular, does it follow that $T$ represented with respect to the basis obtained from $mathcal{B}$ by Gram-Schmidt is also upper-triangular?










share|cite|improve this question













If $T$ is an operator on the finite dimensional vector space $V$ which has a basis $mathcal{B}$ for which the matrix representation of $T$ with this basis is upper-triangular, does it follow that $T$ represented with respect to the basis obtained from $mathcal{B}$ by Gram-Schmidt is also upper-triangular?







linear-algebra matrices inner-product-space gram-schmidt






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share|cite|improve this question











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share|cite|improve this question










asked Nov 13 at 20:35









user193319

2,2862922




2,2862922












  • Let $mathcal{C}$ be the basis obtained from $mathcal{B}$ by Gram-Schmidt. Is the change-of-basis matrix between $mathcal{B}$ and $mathcal{C}$ upper-triangular? (The answer depends somewhat on how exactly you define Gram-Schmidt.) If the answer is "yes", then the answer to your question is "yes" as well, because products and inverses of upper-triangular matrices are upper-triangular.
    – darij grinberg
    Nov 13 at 20:58










  • @darijgrinberg By Gram-Schmidt, I mean by procedure whereby one transforms a basis into an orthonormal basis. Is that what you had in mind, too?
    – user193319
    Nov 13 at 21:00










  • Yes, but there are several of these procedures. In your version, is the $j$-th vector of $mathcal{C}$ a linear combination of the first $j$ vectors of $mathcal{B}$ ? If so, the answer is "yes".
    – darij grinberg
    Nov 13 at 21:02


















  • Let $mathcal{C}$ be the basis obtained from $mathcal{B}$ by Gram-Schmidt. Is the change-of-basis matrix between $mathcal{B}$ and $mathcal{C}$ upper-triangular? (The answer depends somewhat on how exactly you define Gram-Schmidt.) If the answer is "yes", then the answer to your question is "yes" as well, because products and inverses of upper-triangular matrices are upper-triangular.
    – darij grinberg
    Nov 13 at 20:58










  • @darijgrinberg By Gram-Schmidt, I mean by procedure whereby one transforms a basis into an orthonormal basis. Is that what you had in mind, too?
    – user193319
    Nov 13 at 21:00










  • Yes, but there are several of these procedures. In your version, is the $j$-th vector of $mathcal{C}$ a linear combination of the first $j$ vectors of $mathcal{B}$ ? If so, the answer is "yes".
    – darij grinberg
    Nov 13 at 21:02
















Let $mathcal{C}$ be the basis obtained from $mathcal{B}$ by Gram-Schmidt. Is the change-of-basis matrix between $mathcal{B}$ and $mathcal{C}$ upper-triangular? (The answer depends somewhat on how exactly you define Gram-Schmidt.) If the answer is "yes", then the answer to your question is "yes" as well, because products and inverses of upper-triangular matrices are upper-triangular.
– darij grinberg
Nov 13 at 20:58




Let $mathcal{C}$ be the basis obtained from $mathcal{B}$ by Gram-Schmidt. Is the change-of-basis matrix between $mathcal{B}$ and $mathcal{C}$ upper-triangular? (The answer depends somewhat on how exactly you define Gram-Schmidt.) If the answer is "yes", then the answer to your question is "yes" as well, because products and inverses of upper-triangular matrices are upper-triangular.
– darij grinberg
Nov 13 at 20:58












@darijgrinberg By Gram-Schmidt, I mean by procedure whereby one transforms a basis into an orthonormal basis. Is that what you had in mind, too?
– user193319
Nov 13 at 21:00




@darijgrinberg By Gram-Schmidt, I mean by procedure whereby one transforms a basis into an orthonormal basis. Is that what you had in mind, too?
– user193319
Nov 13 at 21:00












Yes, but there are several of these procedures. In your version, is the $j$-th vector of $mathcal{C}$ a linear combination of the first $j$ vectors of $mathcal{B}$ ? If so, the answer is "yes".
– darij grinberg
Nov 13 at 21:02




Yes, but there are several of these procedures. In your version, is the $j$-th vector of $mathcal{C}$ a linear combination of the first $j$ vectors of $mathcal{B}$ ? If so, the answer is "yes".
– darij grinberg
Nov 13 at 21:02















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