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Let $X\subset\mathbb{P}^N$ be a smooth scheme theoretical complete intersection, and $H\subset X$ a linear subspace. Denote by $N_{H,X}$ the normal bundle of $H$ in $X$.

If $\dim(H) = 1$, that is $H$ is a line, then $N_{H,X}$ splits as a sum of line bundles. Does there exists an example with $\dim(H) \geq 2$ in which $N_{H,X}$ does not split as a sum of line bundles?

Thank you.

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1 Answer 1

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For instance, if $X$ is a smooth 4-dimensional quadric in $\mathbb{P}^5$ and $H = \mathbb{P}^2$, the normal bundle fits into the exact sequence $$ 0 \to N_{H/X} \to \mathcal{O}(1)^{\oplus 3} \to \mathcal{O}(2) \to 0, $$ which implies that $$ N_{H/X} \cong \Omega_H(2). $$ In particular, it does not split.

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