Existence of a polynomial not vanishing on subvarietiesIsomorphism including a tensor productProof of Proposition 2.1.1 in Bruns and HerzogEquivalence of weak forms of Hilbert's Nullstellensatz$k$-algebra homomorphism of the polynomial ring $k[x_1,dots,x_n]$Integer polynomials having no common roots in $mathbb C^n$Singular homogeneous polynomialIs the ideal of a variety the annihilator of a subspace of the symmetric algebra?proof: if $K(x_1,ldots,x_k)/K$ is a field extension, and the $x_j$ are algebraically independent over K, M cannot be a finitely generated K-algebraThe existence of a linear map onto an affine algebraic setInequality involving Ideals generated by forms.

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Existence of a polynomial not vanishing on subvarieties


Isomorphism including a tensor productProof of Proposition 2.1.1 in Bruns and HerzogEquivalence of weak forms of Hilbert's Nullstellensatz$k$-algebra homomorphism of the polynomial ring $k[x_1,dots,x_n]$Integer polynomials having no common roots in $mathbb C^n$Singular homogeneous polynomialIs the ideal of a variety the annihilator of a subspace of the symmetric algebra?proof: if $K(x_1,ldots,x_k)/K$ is a field extension, and the $x_j$ are algebraically independent over K, M cannot be a finitely generated K-algebraThe existence of a linear map onto an affine algebraic setInequality involving Ideals generated by forms.













2












$begingroup$


Let $K$ be an algebraically closed field and $X_1,dots,X_m$ be subvarieties of a variety $Xsubset mathbb A^n$. Let $f_1,dots,f_kin K[X]$ such that for every $X_i$ there exists some $f_j$ not vanishing on $X_i$. Prove there exists $g_1,dots,g_k$ such that $sum_a=1^k f_ag_a$ doesn't vanish on $X_i$ for all $i$.










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$endgroup$











  • $begingroup$
    $k$ is an index, so $K$ is the field.
    $endgroup$
    – user26857
    yesterday















2












$begingroup$


Let $K$ be an algebraically closed field and $X_1,dots,X_m$ be subvarieties of a variety $Xsubset mathbb A^n$. Let $f_1,dots,f_kin K[X]$ such that for every $X_i$ there exists some $f_j$ not vanishing on $X_i$. Prove there exists $g_1,dots,g_k$ such that $sum_a=1^k f_ag_a$ doesn't vanish on $X_i$ for all $i$.










share|cite|improve this question











$endgroup$











  • $begingroup$
    $k$ is an index, so $K$ is the field.
    $endgroup$
    – user26857
    yesterday













2












2








2





$begingroup$


Let $K$ be an algebraically closed field and $X_1,dots,X_m$ be subvarieties of a variety $Xsubset mathbb A^n$. Let $f_1,dots,f_kin K[X]$ such that for every $X_i$ there exists some $f_j$ not vanishing on $X_i$. Prove there exists $g_1,dots,g_k$ such that $sum_a=1^k f_ag_a$ doesn't vanish on $X_i$ for all $i$.










share|cite|improve this question











$endgroup$




Let $K$ be an algebraically closed field and $X_1,dots,X_m$ be subvarieties of a variety $Xsubset mathbb A^n$. Let $f_1,dots,f_kin K[X]$ such that for every $X_i$ there exists some $f_j$ not vanishing on $X_i$. Prove there exists $g_1,dots,g_k$ such that $sum_a=1^k f_ag_a$ doesn't vanish on $X_i$ for all $i$.







abstract-algebra commutative-algebra






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited yesterday









user26857

39.3k124183




39.3k124183










asked Mar 3 at 21:34









ryanriessryanriess

654




654











  • $begingroup$
    $k$ is an index, so $K$ is the field.
    $endgroup$
    – user26857
    yesterday
















  • $begingroup$
    $k$ is an index, so $K$ is the field.
    $endgroup$
    – user26857
    yesterday















$begingroup$
$k$ is an index, so $K$ is the field.
$endgroup$
– user26857
yesterday




$begingroup$
$k$ is an index, so $K$ is the field.
$endgroup$
– user26857
yesterday










1 Answer
1






active

oldest

votes


















0












$begingroup$

I suppose your varieties are irreducible. Assume the contrary. Then consider the ideal $I=(f_1,...,f_k)$. Then this implies any element of the ideal vanishes on some $X_i$ and hence is in $mathscr I (X_i)$ for some $i$. Thus you get $Isubset bigcup_i=1 ^n mathscr I(X_i)$. Prime avoidance tells you $I$ is in some $mathscr I(X_i)$ which means each $f_j$ vanishes on $X_i$. Contradiction.






share|cite|improve this answer











$endgroup$












  • $begingroup$
    "ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
    $endgroup$
    – user26857
    yesterday











  • $begingroup$
    surprising how a colloquialism implied disrespect lol
    $endgroup$
    – Soumik Ghosh
    yesterday










  • $begingroup$
    "lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
    $endgroup$
    – user26857
    21 hours ago











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1 Answer
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active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









0












$begingroup$

I suppose your varieties are irreducible. Assume the contrary. Then consider the ideal $I=(f_1,...,f_k)$. Then this implies any element of the ideal vanishes on some $X_i$ and hence is in $mathscr I (X_i)$ for some $i$. Thus you get $Isubset bigcup_i=1 ^n mathscr I(X_i)$. Prime avoidance tells you $I$ is in some $mathscr I(X_i)$ which means each $f_j$ vanishes on $X_i$. Contradiction.






share|cite|improve this answer











$endgroup$












  • $begingroup$
    "ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
    $endgroup$
    – user26857
    yesterday











  • $begingroup$
    surprising how a colloquialism implied disrespect lol
    $endgroup$
    – Soumik Ghosh
    yesterday










  • $begingroup$
    "lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
    $endgroup$
    – user26857
    21 hours ago
















0












$begingroup$

I suppose your varieties are irreducible. Assume the contrary. Then consider the ideal $I=(f_1,...,f_k)$. Then this implies any element of the ideal vanishes on some $X_i$ and hence is in $mathscr I (X_i)$ for some $i$. Thus you get $Isubset bigcup_i=1 ^n mathscr I(X_i)$. Prime avoidance tells you $I$ is in some $mathscr I(X_i)$ which means each $f_j$ vanishes on $X_i$. Contradiction.






share|cite|improve this answer











$endgroup$












  • $begingroup$
    "ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
    $endgroup$
    – user26857
    yesterday











  • $begingroup$
    surprising how a colloquialism implied disrespect lol
    $endgroup$
    – Soumik Ghosh
    yesterday










  • $begingroup$
    "lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
    $endgroup$
    – user26857
    21 hours ago














0












0








0





$begingroup$

I suppose your varieties are irreducible. Assume the contrary. Then consider the ideal $I=(f_1,...,f_k)$. Then this implies any element of the ideal vanishes on some $X_i$ and hence is in $mathscr I (X_i)$ for some $i$. Thus you get $Isubset bigcup_i=1 ^n mathscr I(X_i)$. Prime avoidance tells you $I$ is in some $mathscr I(X_i)$ which means each $f_j$ vanishes on $X_i$. Contradiction.






share|cite|improve this answer











$endgroup$



I suppose your varieties are irreducible. Assume the contrary. Then consider the ideal $I=(f_1,...,f_k)$. Then this implies any element of the ideal vanishes on some $X_i$ and hence is in $mathscr I (X_i)$ for some $i$. Thus you get $Isubset bigcup_i=1 ^n mathscr I(X_i)$. Prime avoidance tells you $I$ is in some $mathscr I(X_i)$ which means each $f_j$ vanishes on $X_i$. Contradiction.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited yesterday









user26857

39.3k124183




39.3k124183










answered yesterday









Soumik GhoshSoumik Ghosh

473110




473110











  • $begingroup$
    "ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
    $endgroup$
    – user26857
    yesterday











  • $begingroup$
    surprising how a colloquialism implied disrespect lol
    $endgroup$
    – Soumik Ghosh
    yesterday










  • $begingroup$
    "lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
    $endgroup$
    – user26857
    21 hours ago

















  • $begingroup$
    "ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
    $endgroup$
    – user26857
    yesterday











  • $begingroup$
    surprising how a colloquialism implied disrespect lol
    $endgroup$
    – Soumik Ghosh
    yesterday










  • $begingroup$
    "lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
    $endgroup$
    – user26857
    21 hours ago
















$begingroup$
"ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
$endgroup$
– user26857
yesterday





$begingroup$
"ur", "u" are more suitable on Facebook. Let's respect this site, and mathematics as well. Thank you!
$endgroup$
– user26857
yesterday













$begingroup$
surprising how a colloquialism implied disrespect lol
$endgroup$
– Soumik Ghosh
yesterday




$begingroup$
surprising how a colloquialism implied disrespect lol
$endgroup$
– Soumik Ghosh
yesterday












$begingroup$
"lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
$endgroup$
– user26857
21 hours ago





$begingroup$
"lol" is also a Facebook way of talking. This is definitely not colloquialism, it's something close to rudeness on a math site. If can't change this attitude I suggest you to go back to Facebook.
$endgroup$
– user26857
21 hours ago


















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