Description of Fano 3-folds as zero loci in a product of (weighted) Grassmannians
In Fano 3-folds from homogeneous vector bundles over Grassmannians De Biase–Fatighenti–Tanturri obtained a description of a general member of each deformation family of Fano 3-folds as the zero locus of a homogeneous vector bundle in a product of Grassmannians and weighted projective spaces. Such description gives new tools to compute cohomological invariants of Fano 3-folds (by virtue of the Borel–Weil–Bott theorem), and gives a representation-theoretic flavour to the classification.
Some of these descriptions are classical (and in fact agree with the usual description of the Fano 3-folds), others were obtained for the Fanosearch project in Quantum periods for 3-dimensional Fano manifolds by Coates–Corti–Galkin–Kasprzyk. In the table below we list the description of De Biase–Fatighenti–Tanturri, using their notation.
| ID | description | ambient variety | homogeneous vector bundle | origin |
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| 1-1 | double cover of $\mathbb{P}^3$ with branch locus a divisor of degree 6
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| 1-2 |
| $\mathbb{P}^4$ | $\mathcal{O}(4)$ | classical |
| 1-3 | complete intersection of quadric and cubic in $\mathbb{P}^5$ | $\mathbb{P}^5$ | $\mathcal{O}(2) \oplus \mathcal{O}(3)$ | classical |
| 1-4 | complete intersection of 3 quadrics in $\mathbb{P}^6$ | $\mathbb{P}^6$ | $\mathcal{O}(2)^{\oplus 3}$ | classical |
| 1-5 | Gushel–Mukai 3-fold
| $\operatorname{Gr}(2,5)$ | $\mathcal{O}(2) \oplus \mathcal{O}(1)^{\oplus2}$ | classical |
| 1-6 | section of half-spinor embedding of a connected component of $\mathrm{OGr}_+(5,10)$ by codimension 7 subspace |
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| 1-7 | section of Plücker embedding of $\mathrm{Gr}(2,6)$ by codimension 5 subspace | $\operatorname{Gr}(2,6)$ | $\mathcal{O}(1)^{\oplus5}$ | classical |
| 1-8 | section of Plücker embedding of $\mathrm{SGr}(3,6)$ by codimension 3 subspace | $\operatorname{Gr}(3,6)$ | $\bigwedge^2\mathcal{U}^{\vee} \oplus \mathcal{O}(1)^{\oplus3}$ | classical |
| 1-9 | section of the adjoint $\mathrm{G}_2$-Grassmannian $\mathrm{G}_2\mathrm{Gr}(2,7)$ by codimension 2 subspace | $\operatorname{Gr}(2,7)$ | $\mathcal{Q}^{\vee}(1) \oplus \mathcal{O}(1)^{\oplus2}$ | classical |
| 1-10 | zero locus of $(\bigwedge^2\mathcal{U}^\vee)^{\oplus 3}$ on $\mathrm{Gr}(3,7)$ | $\operatorname{Gr}(3,7)$ | $(\bigwedge^2\mathcal{U}^\vee)^{\oplus 3}$ | classical |
| 1-11 | double Veronese cone hypersurface of degree 6 in $\mathbb{P}(1,1,1,2,3)$ | $\mathbb{P}(1^3,2,3)$ | $\mathcal{O}(6)$ | classical |
| 1-12 | quartic double solid double cover of $\mathbb{P}^3$ with branch locus a smooth quartic surface
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| 1-13 | hypersurface of degree 3 in $\mathbb{P}^4$ | $\mathbb{P}^4$ | $\mathcal{O}(3)$ | classical |
| 1-14 | complete intersection of 2 quadrics in $\mathbb{P}^5$ | $\mathbb{P}^5$ | $\mathcal{O}(2)^{\oplus 2}$ | classical |
| 1-15 | quintic del Pezzo threefold section of Plücker embedding of $\mathrm{Gr}(2,5)$ by codimension 3 subspace | $\operatorname{Gr}(2,5)$ | $\mathcal{O}(1)^{\oplus 3}$ | classical |
| 1-16 | hypersurface of degree 2 in $\mathbb{P}^4$ | $\mathbb{P}^4$ | $\mathcal{O}(2)$ | classical |
| 1-17 | projective space $\mathbb{P}^3$ | $\mathbb{P}^3$ | classical | |
| 2-1 | blowup of 1-11 in an elliptic curve which is the intersection of two divisors from half the anticanonical linear system | $\mathbb{P}(1^3,2,3) \times \mathbb{P}^1$ | $\mathcal{O}(6,0) \oplus \mathcal{O}(1,1)$ | [CCGK] |
| 2-2 | double cover of 2-34 with branch locus a $(2,4)$-divisor | $\mathbb{P}^1\times \mathbb{P}^2 \times \mathbb{P}^{12}$ | $\mathcal{O}(0,0,2) \oplus K(0,0,1)$ $K \in \operatorname{Ext}_{\mathbb{P}^1 \times \mathbb{P}^2}^2(\mathcal{O}(1,0)^{\oplus 6}, \mathcal{Q}_{\mathbb{P}^2}(-1,-1))$ | [DBFT] |
| 2-3 | blowup of 1-12 in an elliptic curve which is the intersection of two divisors from half the anticanonical linear system |
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| 2-4 | blowup of 1-17 in the intersection of two cubics
| $\mathbb{P}^1 \times \mathbb{P}^3$ | $\mathcal{O}(1,3)$ | [CCGK] |
| 2-5 | blowup of 1-13 in a plane cubic | $\mathbb{P}^1 \times \mathbb{P}^4$ | $\mathcal{O}(0,3) \oplus \mathcal{O}(1,1)$ | [DBFT] |
| 2-6 | Verra 3-fold
| $\mathbb{P}^2 \times \mathbb{P}^2$ | $\mathcal{O}(2,2)$ | [CCGK] |
| 2-7 | blowup of 1-16 in the intersection of two divisors from $|\mathcal{O}_Q(2)|$ | $\mathbb{P}^1 \times \mathbb{P}^4$ | $\mathcal{O}(0,2) \oplus \mathcal{O}(1,2)$ | [CCGK] |
| 2-8 | $\mathbb{P}^2 \times \mathbb{P}^3 \times \mathbb{P}^{12}$ | $\Lambda(0,0,1) \oplus \mathcal{O}(0,0,2)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^2 \times \mathbb{P}^3}(\mathcal{Q}_{\mathbb{P}^3}^{\oplus 3}, \mathcal{Q}_{\mathbb{P}^2}(0, -1))$ | [DBFT] | |
| 2-9 | complete intersection of degree $(1,1)$ and $(2,1)$ in $\mathbb{P}^3\times\mathbb{P}^2$
| $\mathbb{P}^2 \times \mathbb{P}^3$ | $\mathcal{O}(1,1) \oplus \mathcal{O}(1,2)$ | [CCGK] |
| 2-10 | blowup of 1-14 in an elliptic curve which is an intersection of 2 hyperplanes | $\operatorname{Gr}(2,4) \times \mathbb{P}^1$ | $\mathcal{O}(2,0) \oplus \mathcal{O}(1,1)$ | [DBFT] |
| 2-11 | blowup of 1-13 in a line |
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| 2-12 | intersection of 3 $(1,1)$-divisors in $\mathbb{P}^3\times\mathbb{P}^3$
| $\mathbb{P}^3 \times \mathbb{P}^3$ | $\mathcal{O}(1,1)^{\oplus 3}$ | [CCGK] |
| 2-13 | blowup of 1-16 in a curve of degree 6 and genus 2 | $\mathbb{P}^2 \times \mathbb{P}^4$ | $\mathcal{O}(1,1)^{\oplus 2} \oplus \mathcal{O}(0,2)$ | [CCGK] |
| 2-14 | blowup of 1-15 in an elliptic curve which is an intersection of 2 hyperplanes | $\operatorname{Gr}(2,5) \times \mathbb{P}^1$ | $\mathcal{O}(1,0)^{\oplus 3} \oplus \mathcal{O}(1,1)$ | [CCGK] |
| 2-15 |
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| 2-16 | blowup of 1-14 in a conic |
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| 2-17 | blowup of 1-16 in an elliptic curve of degree 5 |
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| 2-18 | double cover of 2-34 with branch locus a divisor of degree $(2,2)$ | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^6$ | $\Lambda(0,0,1) \oplus \mathcal{O}(0,0,2)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^2}(\mathcal{Q}_{\mathbb{P}^2}^{\oplus 2}, \mathcal{O}(1,-1))$ | [DBFT] |
| 2-19 | blowup of 1-14 in a line |
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| 2-20 | blowup of 1-15 in a twisted cubic | $\operatorname{Gr}(2,5) \times \mathbb{P}^2$ | $\mathcal{U}^{\vee}_{\operatorname{Gr}(2,5)}(0,1) \oplus \mathcal{O}(1,0)^{\oplus 3}$ | [CCGK] |
| 2-21 | blowup of 1-16 in a twisted quartic | $\operatorname{Gr}(2,4) \times \mathbb{P}^4$ | $\mathcal{U}^{\vee}_{\operatorname{Gr}(2,4)}(0,1)^{\oplus 2} \oplus \mathcal{O}(1,0)$ | [CCGK] |
| 2-22 | blowup of 1-15 in a conic |
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| 2-23 |
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| 2-24 | divisor on $\mathbb{P}^2\times\mathbb{P}^2$ of bidegree $(1,2)$ | $\mathbb{P}^2 \times \mathbb{P}^2$ | $\mathcal{O}(1,2)$ | classical |
| 2-25 | blowup of 1-17 in an elliptic curve which is an intersection of 2 quadrics
| $\mathbb{P}^1 \times \mathbb{P}^3$ | $\mathcal{O}(1,2)$ | [CCGK] |
| 2-26 | blowup of 1-15 in a line |
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| 2-27 | blowup of 1-17 in a twisted cubic | $\mathbb{P}^3 \times \mathbb{P}^2$ | $\mathcal{O}(1,1)^{\oplus 2}$ | [CCGK] |
| 2-28 | blowup of 1-17 in a plane cubic | $\mathbb{P}^3 \times \mathbb{P}^{10}$ | $\Lambda(0,1) \oplus \mathcal{O}(1,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^3}(\operatorname{Sym}^2\mathcal{Q}, \mathcal{Q}(-1))$ | [DBFT] |
| 2-29 | blowup of 1-16 in a conic | $\mathbb{P}^1 \times \mathbb{P}^4$ | $\mathcal{O}(0,2) \oplus \mathcal{O}(1,1)$ | [DBFT] |
| 2-30 | blowup of 1-17 in a conic |
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| 2-31 | blowup of 1-16 in a line | $\mathbb{P}^2 \times \operatorname{Gr}(2,4)$ | $\mathcal{U}^{\vee}_{\operatorname{Gr}(2,4)}(1,0) \oplus \mathcal{O}(0,1)$ | [DBFT] |
| 2-32 | divisor on $\mathbb{P}^2\times\mathbb{P}^2$ of bidegree $(1,1)$
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| 2-33 | blowup of 1-17 in a line | $\mathbb{P}^1 \times \mathbb{P}^3$ | $\mathcal{O}(1,1)$ | [DBFT] |
| 2-34 | $\mathbb{P}^1\times\mathbb{P}^2$ | $\mathbb{P}^1 \times \mathbb{P}^2$ | classical | |
| 2-35 | $\mathrm{Bl}_p\mathbb{P}^3$
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| 2-36 | $\mathbb{P}(\mathcal{O}_{\mathbb{P}^2}\oplus\mathcal{O}_{\mathbb{P}^2}(2))$ | $\mathbb{P}^2 \times \mathbb{P}^6$ | $\Lambda(0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^2}(\operatorname{Sym}^2\mathcal{Q}, \mathcal{Q}(-1))$ | [DBFT] |
| 3-1 | double cover of 3-27 with branch locus a divisor of degree $(2,2,2)$ | $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^8$ | $K(0,0,0,1) \oplus \mathcal{O}(0,0,0,2)$ $K \in \operatorname{Ext}^2_{(\mathbb{P}^1)^3}(\mathcal{O}(0,0,1)^{\oplus 4},\mathcal{O}(1,-1,-1))$ | [DBFT] |
| 3-2 | divisor from $|\mathcal{L}^{\otimes 2}\otimes\mathcal{O}(2,3)|$ on the $\mathbb{P}^2$-bundle $\mathbb{P}(\mathcal{O}\oplus\mathcal{O}(-1,-1)^{\oplus 2})$ over $\mathbb{P}^1\times\mathbb{P}^1$ such that $X\cap Y$ is irreducible, and $\mathcal{L}$ is the tautological bundle, and $Y\in|\mathcal{L}|$ | $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^5$ | $\Lambda(0,0,1) \oplus \mathcal{O}(0,1,2)$ $\Lambda \in \operatorname{Ext}^1_{(\mathbb{P}^1)^2}(\mathcal{O}(0,1)^{\oplus 2}, \mathcal{O}(1, -1))$ | [DBFT] |
| 3-3 | divisor on $\mathbb{P}^1\times\mathbb{P}^1\times\mathbb{P}^2$ of degree $(1,1,2)$ | $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^2$ | $\mathcal{O}(1,1,2)$ | [CCGK] |
| 3-4 | blowup of 2-18 in a smooth fiber of the composition of the projection to $\mathbb{P}^1\times\mathbb{P}^2$ with the projection to $\mathbb{P}^2$ of the double cover with the projection | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^6 \times \mathbb{P}^1$ | $\Lambda(0,0,1,0) \oplus \mathcal{O}(0,0,2,0) \oplus \mathcal{O}(0,1,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^2}(\mathcal{Q}_{\mathbb{P}^2}^{\oplus 2}, \mathcal{O}(1,-1))$ | [DBFT] |
| 3-5 | blowup of 2-34 in a curve $C$ of degree $(5,2)$ such that $C\hookrightarrow\mathbb{P}^1\times\mathbb{P}^2\to\mathbb{P}^2$ is an embedding | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^7$ | $\Lambda(0,0,1) \oplus \mathcal{O}(0,1,1)^{\oplus 2}$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^2}(\mathcal{Q}_{\mathbb{P}^2}^{\oplus 2}, \mathcal{O}(1,-1))$ | [DBFT] |
| 3-6 | blowup of 1-17 in the disjoint union of a line and an elliptic curve of degree 4
| $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^3$ | $\mathcal{O}(1,0,2) \oplus \mathcal{O}(0,1,1)$ | [DBFT] |
| 3-7 | blowup of 2-32 in an elliptic curve which is the intersection of two divisors from $|-\frac{1}{2}\mathrm{K}_W|$ | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^2$ | $\mathcal{O}(0,1,1) \oplus \mathcal{O}(1,1,1)$ | [CCGK] |
| 3-8 | divisor from the linear system $|(\alpha\circ\pi_1)^*(\mathcal{O}_{\mathbb{P}^2}(1)\otimes\pi_2^*(\mathcal{O}_{\mathbb{P}^2}(2))|$ where $\pi_i\colon\mathrm{Bl}_1\mathbb{P}^2\times\mathbb{P}^2\to\mathrm{Bl}_1\mathbb{P}^2,\mathbb{P}^2$ are the projections, and $\alpha\colon\mathrm{Bl}_1\mathbb{P}^2\to\mathbb{P}^2$ is the blowup | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^2$ | $\mathcal{O}(0,1,2) \oplus \mathcal{O}(1,1,0)$ | [DBFT] |
| 3-9 | blowup of the cone over the Veronese of $\mathbb{P}^2$ in $\mathbb{P}^5$ with center the disjoint union of the vertex and a quartic curve on $\mathbb{P}^2$ | $\mathbb{P}^2 \times \mathbb{P}^6 \times \mathbb{P}^{20}$ | $\Lambda(0,1,0) \oplus \mathcal{Q}_{\mathbb{P}^6}(0,0,1) \oplus K(0,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^2}(\operatorname{Sym}^2\mathcal{Q}, \mathcal{Q}(-1))$, $K \in \operatorname{Ext}^3_{\mathbb{P}^2}(\operatorname{Sym}^4\mathcal{Q}, \mathcal{Q}(-3))$ | [DBFT] |
| 3-10 | blowup of 1-16 in the disjoint union of 2 conics
| $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^4$ | $\mathcal{O}(1,0,1) \oplus \mathcal{O}(0,1,1) \oplus \mathcal{O}(0,0,2)$ | [DBFT] |
| 3-11 | blowup of 2-35 in an elliptic curve which is the intersection of two divisors from $|-\frac{1}{2}\mathrm{K}_{V_7}|$ | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^3$ | $\mathcal{O}(1,1,1) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,1)$ | [DBFT] |
| 3-12 | blowup of 1-17 in the disjoint union of a line and a twisted cubic | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^3$ | $\mathcal{O}(0,1,1) \oplus \mathcal{O}(0,1,1) \oplus \mathcal{O}(1,0,1)$ | [DBFT] |
| 3-13 | blowup of 2-32 in a curve $C$ of bidegree $(2,2)$ such that the composition $C\hookrightarrow W\hookrightarrow\mathbb{P}^2\times\mathbb{P}^2\overset{p_i}{\to}\mathbb{P}^2$ is an embedding for $i=1,2$ | $(\mathbb{P}^2)^3$ | $\mathcal{O}(1,1,0) \oplus \mathcal{O}(1,0,1) \oplus \mathcal{O}(0,1,1)$ | [CCGK] |
| 3-14 | blowup of 1-17 in the disjoint union of a plane cubic curve and a point outside the plane | $\mathbb{P}^3 \times \mathbb{P}^{10} \times \mathbb{P}^2$ | $\Lambda(0,1,0) \oplus \mathcal{Q}_{\mathbb{P}^2}(1,0,0) \oplus \mathcal{O}(1,1,0)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^3}(\operatorname{Sym}^2\mathcal{Q}, \mathcal{Q}(-1)) $ | [DBFT] |
| 3-15 | blowup of 1-16 in the disjoint union of a line and a conic | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^4$ | $\mathcal{O}(1,0,1) \oplus \mathcal{O}(0,1,1) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,1)$ | [DBFT] |
| 3-16 | blowup of 2-35 in the proper transform of a twisted cubic containing the center of the blowup | $\mathbb{P}^2_1 \times \mathbb{P}^2_2 \times \mathbb{P}^3$ | $\mathcal{O}(0,1,1) \oplus \mathcal{O}(1,1,0) \oplus \mathcal{Q}_{\mathbb{P}^2_1}(0,0,1)$ | [DBFT] |
| 3-17 | divisor on $\mathbb{P}^1\times\mathbb{P}^1\times\mathbb{P}^2$ of degree $(1,1,1)$ | $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^2$ | $\mathcal{O}(1,1,1)$ | [CCGK] |
| 3-18 | blowup of 1-17 in the disjoint union of a line and a conic |
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| 3-19 | blowup of 1-16 in two non-collinear points | $\mathbb{P}^2 \times \mathbb{P}^4$ | $\mathcal{O}(0,2) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,1)$ | [DBFT] |
| 3-20 | blowup of 1-16 in the disjoint union of two lines | $\mathbb{P}^2_1 \times \mathbb{P}^2_2 \times \mathbb{P}^4$ | $\mathcal{O}(1,1,0) \oplus \mathcal{Q}_{\mathbb{P}^2_1}(0,0,1) \oplus \mathcal{Q}_{\mathbb{P}^2_2}(0,0,1)$ | [DBFT] |
| 3-21 | blowup of 2-34 in a curve of degree $(2,1)$ | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^6$ | $\mathcal{O}(0,1,1) \oplus \Lambda(0,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^2}(\mathcal{Q}_{\mathbb{P}^2}^{\oplus 2}, \mathcal{O}(1,-1)) $ | [DBFT] |
| 3-22 | blowup of 2-34 in a conic on $\{x\}\times\mathbb{P}^2$, $x\in\mathbb{P}^1$ | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^6$ | $\mathcal{O}(1,0,1) \oplus \Lambda(0,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^2}(\operatorname{Sym}^2 \mathcal{Q}, \mathcal{Q}(-1))$ | [DBFT] |
| 3-23 | blowup of 2-35 in the proper transform of a conic containing the center of the blowup | $\mathbb{P}^2 \times \mathbb{P}^3 \times \mathbb{P}^4$ | $\mathcal{Q}_{\mathbb{P}^2}(0,1,0) \oplus \mathcal{O}(1,0,1) \oplus \mathcal{Q}_{\mathbb{P}^3}(0,0,1)$ | [DBFT] |
| 3-24 | the fiber product of 2-32 with $\mathrm{Bl}_p\mathbb{P}^2$ over $\mathbb{P}^2$
| $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^2$ | $\mathcal{O}(1,1,0) \oplus \mathcal{O}(0,1,1)$ | [CCGK] |
| 3-25 | blowup of 1-17 in the disjoint union of two lines
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| 3-26 | blowup of 1-17 in the disjoint union of a point and a line
| $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^3$ | $\mathcal{O}(1,0,1) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,1)$ | [DBFT] |
| 3-27 | $\mathbb{P}^1\times\mathbb{P}^1\times\mathbb{P}^1$ | $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^1$ | classical | |
| 3-28 | $\mathbb{P}^1\times\mathrm{Bl}_p\mathbb{P}^2$ | $\mathbb{P}^1 \times \mathbb{P}^1 \times \mathbb{P}^2$ | $\mathcal{O}(1,0,1)$ | [DBFT] |
| 3-29 | blowup of 2-35 in a line on the exceptional divisor | $\mathbb{P}^3 \times \mathbb{P}^2 \times \mathbb{P}^9$ | $\mathcal{Q}_{\mathbb{P}^2}(1,0,0) \oplus \mathcal{Q}_{\mathbb{P}^3}(0,0,1) \oplus\Lambda(0,0,1) \oplus \mathcal{O}(0,-1,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^2}(\operatorname{Sym}^2\mathcal{Q}, \mathcal{Q}(-1))$ | [DBFT] |
| 3-30 | blowup of 2-35 in the proper transform of a line containing the center of the blowup
| $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^3$ | $\mathcal{O}(1,1,0) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,1)$ | [DBFT] |
| 3-31 | blowup of the cone over a smooth quadric in $\mathbb{P}^3$ in the vertex
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| 4-1 | divisor on $\mathbb{P}^1\times\mathbb{P}^1\times\mathbb{P}^1\times\mathbb{P}^1$ of degree $(1,1,1,1)$ | $(\mathbb{P}^1)^4$ | $\mathcal{O}(1,1,1,1)$ | classical |
| 4-2 | blowup of the cone over a smooth quadric in $\mathbb{P}^3$ in the disjoint union of the vertex and an elliptic curve on the quadric | $\mathbb{P}^3 \times \mathbb{P}^4 \times \mathbb{P}^5$ | $\mathcal{Q}_{\mathbb{P}^3}(0,1,0) \oplus \mathcal{Q}_{\mathbb{P}^4}(0,0,1) \oplus \mathcal{O}(2,0,0) \oplus \mathcal{O}(0,1,1)$ | [DBFT] |
| 4-3 | blowup of 3-27 in a curve of degree $(1,1,2)$ | $(\mathbb{P}^1)^3 \times \mathbb{P}^2$ | $\mathcal{O}(1,1,0,1) \oplus \mathcal{O}(0,0,1,1)$ | [DBFT] |
| 4-4 | blowup of 3-19 in the proper transform of a conic through the points | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^4$ | $\mathcal{O}(1,1,0) \oplus \mathcal{O}(0,0,2) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,1)$ | [DBFT] |
| 4-5 | blowup of 2-34 in the disjoint union of a curve of degree $(2,1)$ and a curve of degree $(1,0)$ | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^6 \times \mathbb{P}^1$ | $\mathcal{O}(0,1,1,0) \oplus \Lambda(0,0,1,0) \oplus \mathcal{O}(0,1,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^2}(\mathcal{Q}_{\mathbb{P}^2}^{\oplus 2},\mathcal{O}(1,-1))$ | [DBFT] |
| 4-6 | blowup of 1-17 in the disjoint union of 3 lines
| $(\mathbb{P}^1)^3 \times \mathbb{P}^3$ | $\mathcal{O}(1,0,0,1) \oplus \mathcal{O}(0,1,0,1) \oplus \mathcal{O}(0,0,1,1)$ | [DBFT] |
| 4-7 | blowup of 2-32 in the disjoint union of a curve of degree $(0,1)$ and a curve of degree $(1,0)$ |
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| 4-8 | blowup of 3-27 in a curve of degree $(0,1,1)$ |
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| 4-9 | blowup of 3-25 in an exceptional curve of the blowup | $(\mathbb{P}^1)^2 \times \mathbb{P}^2 \times \mathbb{P}^3$ | $\mathcal{O}(1,0,1,0) \oplus \mathcal{O}(0,1,0,1) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,0,1)$ | [DBFT] |
| 4-10 | $\mathbb{P}^1\times\mathrm{Bl}_2\mathbb{P}^2$ |
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| 4-11 | blowup of 3-28 in $\{x\}\times E$, $x\in\mathbb{P}^1$ and $E$ the $(-1)$-curve | $\mathbb{P}^1 \times \mathbb{P}^2 \times \mathbb{P}^1 \times \mathbb{P}^6$ | $\mathcal{O}(0,1,1,0) \oplus \mathcal{Q}_{\mathbb{P}^2}(0,0,0,1) \oplus\Lambda(0,0,0,1) \oplus \mathcal{O}(0,0,-1,1)$ $\Lambda \in \operatorname{Ext}^1_{(\mathbb{P}^1)^2}(\mathcal{O}(0,1)^{\oplus 2}, \mathcal{O}(1, -1))$ | [DBFT] |
| 4-12 | blowup of 2-33 in the disjoint union of two exceptional lines of the blowup | $ \mathbb{P}^1 \times \mathbb{P}^3 \times \mathbb{P}^{8}$ | $\mathcal{O}(1,1,0) \oplus \Lambda(0,0,1) \oplus \mathcal{O}(-1,1,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^3}(\mathcal{Q}_{\mathbb{P}^3}^{\oplus 2},\mathcal{O}(1,-1))$ | [DBFT] |
| 4-13 | blowup of 3-27 in a curve of degree $(1,1,3)$ | $ \mathbb{P}^1_1 \times \mathbb{P}^1_2 \times \mathbb{P}^1_3 \times \mathbb{P}^4$ | $\Lambda(0,0,0,1) \oplus \mathcal{O}(1,0,1,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1_1 \times \mathbb{P}^1_2}(\mathcal{O}(0,1)^{\oplus 2}, \mathcal{O}(1, -1))$ | [DBFT] |
| 5-1 | blowup of 2-29 in the disjoint union of three exceptional lines of the blowup | $\mathbb{P}^1 \times \mathbb{P}^3 \times \mathbb{P}^{8} \times \mathbb{P}^{11}$ | $\mathcal{O}(1,1,0,0) \oplus \Lambda(0,0,1,0) \oplus \mathcal{O}(-1,1,1,0) \oplus \mathcal{Q}_{\mathbb{P}^3}(0,0,0,1) \oplus \mathcal{Q}_{\mathbb{P}^8}(0,0,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^3}(\mathcal{Q}_{\mathbb{P}^3}^{\oplus 2},\mathcal{O}(1,-1))$ | [DBFT] |
| 5-2 | blowup of 3-25 in the disjoint union of two exceptional lines on the same irreducible component | $\mathbb{P}^1 \times \mathbb{P}^3 \times \mathbb{P}^{8} \times \mathbb{P}^1$ | $\mathcal{O}(1,1,0,0) \oplus \Lambda(0,0,1,0) \oplus \mathcal{O}(-1,1,1,0) \oplus \mathcal{O}(0,1,0,1)$ $\Lambda \in \operatorname{Ext}^1_{\mathbb{P}^1 \times \mathbb{P}^3}(\mathcal{Q}_{\mathbb{P}^3}^{\oplus 2},\mathcal{O}(1,-1))$ | [DBFT] |
| 5-3 | $\mathbb{P}^1\times\mathrm{Bl}_3\mathbb{P}^2$ |
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| 6-1 | $\mathbb{P}^1\times\mathrm{Bl}_4\mathbb{P}^2$ | $\operatorname{Gr}(2,5) \times \mathbb{P}^1$ | $\mathcal{O}(1,0)^{\oplus 4}$ | classical |
| 7-1 | $\mathbb{P}^1\times\mathrm{Bl}_5\mathbb{P}^2$ | $\mathbb{P}^4 \times \mathbb{P}^1$ | $\mathcal{O}(2,0)^{\oplus 2}$ | classical |
| 8-1 | $\mathbb{P}^1\times\mathrm{Bl}_6\mathbb{P}^2$ | $\mathbb{P}^3 \times \mathbb{P}^1$ | $\mathcal{O}(3,0)$ | classical |
| 9-1 | $\mathbb{P}^1\times\mathrm{Bl}_7\mathbb{P}^2$ |
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| 10-1 | $\mathbb{P}^1\times\mathrm{Bl}_8\mathbb{P}^2$ | $\mathbb{P}(1^2,2,3) \times \mathbb{P}^1$ | $\mathcal{O}(6,0)$ | classical |