When is a set of vectors in $mathbb{C}^n$ where the $n$th component of each vector is the $(n-1)$st power of...












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Suppose $alpha_1,alpha_2,dots,alpha_n in mathbb{C}$. Consider the set of vectors $S = {xin mathbb{C}^n : x = (1, alpha_i, alpha^2_i, dots,alpha^{n-1}_i), 1leq i leq n }$. Under what conditions on $alpha_1, alpha_2, dots , alpha_n$ is $S$ linearly dependent?










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  • 2




    $begingroup$
    If and only if $alpha_i = alpha_j$ for some $ine j$. See en.wikipedia.org/wiki/Vandermonde_matrix.
    $endgroup$
    – Song
    Jan 12 at 16:24










  • $begingroup$
    @DavidC.Ullrich Thanks, edited
    $endgroup$
    – Fortox
    Jan 12 at 16:37










  • $begingroup$
    If it's not clear why it matters consider a simpler example: (i) If $ainBbb R$ then ${xinBbb R:xge a}=[a,infty)$. (ii) Otoh ${xinBbb R:ainBbb R. xge a}=Bbb R$. (Because in the second example there's a "such that $ainBbb R$" inside the braces; for any $x$ there is $a$ such that $xge a$.)
    $endgroup$
    – David C. Ullrich
    Jan 12 at 16:48


















1












$begingroup$


Suppose $alpha_1,alpha_2,dots,alpha_n in mathbb{C}$. Consider the set of vectors $S = {xin mathbb{C}^n : x = (1, alpha_i, alpha^2_i, dots,alpha^{n-1}_i), 1leq i leq n }$. Under what conditions on $alpha_1, alpha_2, dots , alpha_n$ is $S$ linearly dependent?










share|cite|improve this question











$endgroup$








  • 2




    $begingroup$
    If and only if $alpha_i = alpha_j$ for some $ine j$. See en.wikipedia.org/wiki/Vandermonde_matrix.
    $endgroup$
    – Song
    Jan 12 at 16:24










  • $begingroup$
    @DavidC.Ullrich Thanks, edited
    $endgroup$
    – Fortox
    Jan 12 at 16:37










  • $begingroup$
    If it's not clear why it matters consider a simpler example: (i) If $ainBbb R$ then ${xinBbb R:xge a}=[a,infty)$. (ii) Otoh ${xinBbb R:ainBbb R. xge a}=Bbb R$. (Because in the second example there's a "such that $ainBbb R$" inside the braces; for any $x$ there is $a$ such that $xge a$.)
    $endgroup$
    – David C. Ullrich
    Jan 12 at 16:48
















1












1








1





$begingroup$


Suppose $alpha_1,alpha_2,dots,alpha_n in mathbb{C}$. Consider the set of vectors $S = {xin mathbb{C}^n : x = (1, alpha_i, alpha^2_i, dots,alpha^{n-1}_i), 1leq i leq n }$. Under what conditions on $alpha_1, alpha_2, dots , alpha_n$ is $S$ linearly dependent?










share|cite|improve this question











$endgroup$




Suppose $alpha_1,alpha_2,dots,alpha_n in mathbb{C}$. Consider the set of vectors $S = {xin mathbb{C}^n : x = (1, alpha_i, alpha^2_i, dots,alpha^{n-1}_i), 1leq i leq n }$. Under what conditions on $alpha_1, alpha_2, dots , alpha_n$ is $S$ linearly dependent?







linear-algebra






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share|cite|improve this question













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edited Jan 12 at 16:36







Fortox

















asked Jan 12 at 16:21









FortoxFortox

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  • 2




    $begingroup$
    If and only if $alpha_i = alpha_j$ for some $ine j$. See en.wikipedia.org/wiki/Vandermonde_matrix.
    $endgroup$
    – Song
    Jan 12 at 16:24










  • $begingroup$
    @DavidC.Ullrich Thanks, edited
    $endgroup$
    – Fortox
    Jan 12 at 16:37










  • $begingroup$
    If it's not clear why it matters consider a simpler example: (i) If $ainBbb R$ then ${xinBbb R:xge a}=[a,infty)$. (ii) Otoh ${xinBbb R:ainBbb R. xge a}=Bbb R$. (Because in the second example there's a "such that $ainBbb R$" inside the braces; for any $x$ there is $a$ such that $xge a$.)
    $endgroup$
    – David C. Ullrich
    Jan 12 at 16:48
















  • 2




    $begingroup$
    If and only if $alpha_i = alpha_j$ for some $ine j$. See en.wikipedia.org/wiki/Vandermonde_matrix.
    $endgroup$
    – Song
    Jan 12 at 16:24










  • $begingroup$
    @DavidC.Ullrich Thanks, edited
    $endgroup$
    – Fortox
    Jan 12 at 16:37










  • $begingroup$
    If it's not clear why it matters consider a simpler example: (i) If $ainBbb R$ then ${xinBbb R:xge a}=[a,infty)$. (ii) Otoh ${xinBbb R:ainBbb R. xge a}=Bbb R$. (Because in the second example there's a "such that $ainBbb R$" inside the braces; for any $x$ there is $a$ such that $xge a$.)
    $endgroup$
    – David C. Ullrich
    Jan 12 at 16:48










2




2




$begingroup$
If and only if $alpha_i = alpha_j$ for some $ine j$. See en.wikipedia.org/wiki/Vandermonde_matrix.
$endgroup$
– Song
Jan 12 at 16:24




$begingroup$
If and only if $alpha_i = alpha_j$ for some $ine j$. See en.wikipedia.org/wiki/Vandermonde_matrix.
$endgroup$
– Song
Jan 12 at 16:24












$begingroup$
@DavidC.Ullrich Thanks, edited
$endgroup$
– Fortox
Jan 12 at 16:37




$begingroup$
@DavidC.Ullrich Thanks, edited
$endgroup$
– Fortox
Jan 12 at 16:37












$begingroup$
If it's not clear why it matters consider a simpler example: (i) If $ainBbb R$ then ${xinBbb R:xge a}=[a,infty)$. (ii) Otoh ${xinBbb R:ainBbb R. xge a}=Bbb R$. (Because in the second example there's a "such that $ainBbb R$" inside the braces; for any $x$ there is $a$ such that $xge a$.)
$endgroup$
– David C. Ullrich
Jan 12 at 16:48






$begingroup$
If it's not clear why it matters consider a simpler example: (i) If $ainBbb R$ then ${xinBbb R:xge a}=[a,infty)$. (ii) Otoh ${xinBbb R:ainBbb R. xge a}=Bbb R$. (Because in the second example there's a "such that $ainBbb R$" inside the braces; for any $x$ there is $a$ such that $xge a$.)
$endgroup$
– David C. Ullrich
Jan 12 at 16:48












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