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Linear sections of Segre varieties and rational normal scrolls

The scroll $S_{(1,k)}$ can be locally parametrized by the map $$ \begin{array}{cccc} \phi: & \mathbb{A}^1\times\mathbb{P}^1 & \longrightarrow & \mathbb{P}^{k+2}\\ & (u,[\alpha_0:\alpha_1]) & \mapsto …
Puzzled's user avatar
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1 vote

If $X$ is an affine variety, is $X$ one component of a complete intersection with two?

I will consider the projective closure $X\subset\mathbb{P}^n$. Let say that $X$ is scheme theoretically defined by equations of degree $d_1\geq d_2\geq ... \geq d_m$. Then we can find $f_i \in H^0(X,\m …
Puzzled's user avatar
  • 8,998
1 vote
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Surface of type $(2,2)$ on the Segre cubic scroll $\mathbb{P}^1 \times \mathbb{P}^2 \subset ...

Here is another approach. Take a smooth surface $X$ of type $(d,2)$ in $S$. The general fiber of the projection $\pi:X\rightarrow \mathbb{P}^1$ is a smooth conic. So $X$ is rationally connected and si …
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