Local Hartshorne conjecture for varieties covered by lines

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Let X⊂PNX\subset {\mathbb P}^N be covered by lines, let x∈Xx\in X be a general point, and let Lx⊂Pn−1\mathcal L_x\subset {\mathbb P}^{n-1} be the variety of lines through xx. Let TT be the span of Lx\mathcal L_x in Pn−1{\mathbb P}^{n-1}. Local Hartshorne conjecture. If

dim⁡(Lx)⩾n−12\dim(\mathcal L_x)\geqslant \frac{n-1}{2}

and

dim⁡(Lx)>2codim⁡(Lx,T),\dim(\mathcal L_x)>2\operatorname{codim}(\mathcal L_x,T),

then Lx⊂Pn−1\mathcal L_x\subset {\mathbb P}^{n-1} is a complete intersection. This is proposed as a weaker, local version of Hartshorne's conjecture for Fano manifolds covered by lines; the source does not give a resolution.

References

Primary source

Paltin Ionescu and Francesco Russo, “Manifolds covered by lines and the Hartshorne Conjecture for quadratic manifolds”, arXiv:1209.2047 (2012).

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