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Complex geometry is the study of complex manifolds, complex algebraic varieties, complex analytic spaces, and, by extension, of almost complex structures. It is a part of differential geometry, algebraic geometry and analytic geometry.

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0 answers
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Kelly's theorem for quadratic polynomials

Let $f_1, \ldots, f_m$ be homogeneous irreducible quadratic polynomials in $\mathbb{C}[x_1, \ldots, x_n]$. Assume that these polynomials are pairwise coprime. Denote $P:= f_1 \cdot f_2 \ldots \cdo …
Alexey Milovanov's user avatar
10 votes
1 answer
411 views

Kelly's theorem about a resolution of the Sylvester–Gallai problem

Kelly's theorem states: Every finite point set of complex space such that the line joining any two points from this set contains at least one more point from this set (every Sylvester-Gallai configara …
Alexey Milovanov's user avatar
2 votes
Accepted

Kelly's theorem about a resolution of the Sylvester–Gallai problem

I have found: https://arxiv.org/abs/1211.0330 Also https://arxiv.org/pdf/math/0403023.pdf (thank to Mike Miller).
Alexey Milovanov's user avatar
0 votes
0 answers
288 views

Union of varieties

Let $Q_1, \ldots, Q_k$ and $P_1,\ldots, P_m$ be irredicable homogenous polynomials in $\mathbb{C}[x_0,\ldots, x_n]$ such that $V(Q_1, \ldots, Q_k) \subseteq \cup_i V(P_i)$. Here $V$ is projective vari …
Alexey Milovanov's user avatar
2 votes
0 answers
205 views

Sylvester-Gallai-type theorem for quadratic polynomials

Let $F_1, F_2$ and $F_3$ be finites sets of irreducible polynomials in $\mathbb{C}[x_0, \ldots, x_n]$ of degree at most $2$ such that $F_1 \cap F_2 \cap F_3 = \varnothing$ and for every $Q_1, Q_2$ fr …
Alexey Milovanov's user avatar
2 votes
3 answers
331 views

Linear homogenous polynomials that generates one quadratic polynomial

Let $P_1, \ldots, P_m$, $Q_1, \ldots, Q_k \in \mathbb{C}[x_0,\ldots,x_n]$ be linear homogenous polynomials. Let $f$ be a homogenous quadratic polynomial of degree $2$. Assume that for every $i$ and f …
Alexey Milovanov's user avatar
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Accepted

Linear homogenous polynomials that generates one quadratic polynomial

We will assume that $f$ is irreducible (if $f$ is not irreducible then in fact the argument of Zach Teitler's answer works). Consider $M:= f \cap P_1$ (I mean the intersection of the zeros $f$ and $P …
Alexey Milovanov's user avatar
0 votes
Accepted

Linear homogenous polynomials that generates several quadratic polynomials

Yes. 1) A quadratic homogenous polynomial $f$ (over $\mathbb{C}$) is irreducible iff $\text{rk}(f) \ge 3$. Here $\text{rk}(f)$ is the rank of $f$ as a quadratic form. Indeed, if $\text{rk}(f) < 3$ …
Alexey Milovanov's user avatar
3 votes
1 answer
240 views

Linear homogenous polynomials that generates several quadratic polynomials

This is a generalization of this question. Let $P_1, \ldots, P_m$, $Q_1, \ldots, Q_k \in \mathbb{C}[x_0,\ldots,x_n]$ be linear homogenous polynomials. Let $f_1, \ldots, f_s$ be a homogenous quadrati …
Alexey Milovanov's user avatar