Fanography

A tool to visually study the geography of Fano 3-folds.

Identification

Fano variety 3-18

blowup of 1-17 in the disjoint union of a line and a conic

Picard rank
3 (others)
$-\mathrm{K}_X^3$
36
$\mathrm{h}^{1,2}(X)$
0
Hodge diamond
1
0 0
0 3 0
0 0 0 0
0 3 0
0 0
1
1
0 3
0 0 15
0 0 0 21
0 0 0
0 0
0
Anticanonical bundle
index
1
$\dim\mathrm{H}^0(X,\omega_X^\vee)$
21
$-\mathrm{K}_X$ very ample?
yes
$-\mathrm{K}_X$ basepoint free?
yes
hyperelliptic
no
trigonal
no
Birational geometry

This variety is rational.


This variety is the blowup of

  • 2-29, in a curve of genus 0
  • 2-30, in a curve of genus 0
  • 2-33, in a curve of genus 0

This variety can be blown up (in a curve) to

  • 4-4, in a curve of genus 0
Deformation theory
number of moduli
0

$\mathrm{Aut}^0(X)$ $\dim\mathrm{Aut}^0(X)$ number of moduli
$\mathrm{B}\times\mathbb{G}_{\mathrm{m}}$ 3 0
Period sequence

The following period sequences are associated to this Fano 3-fold:

GRDB
#41
Fanosearch
#160
Extremal contractions
Semiorthogonal decompositions

A full exceptional collection can be constructed using Orlov's blowup formula.

Structure of quantum cohomology

Generic semisimplicity of:

  • small quantum cohomology, proved by Ciolli in 2005, see [MR2168069] , using the description of a 1 or 2-curve blowup of $\mathbb{P}^3$ or $Q^3$
Zero section description

Fano 3-folds from homogeneous vector bundles over Grassmannians gives the following description(s):

variety
$\mathbb{P}^1\times \mathbb{P}^3 \times \mathbb{P}^4$
bundle
$\mathcal{O}(1,1,0) \oplus \mathcal{O}(0,1,1) \oplus \mathcal{Q}_{\mathbb{P}^3}(0,0,1)$


variety
$\mathbb{P}^1 \times \operatorname{Fl}(1,2,5)$
bundle
$\mathcal{Q}_2(0;0,0) \oplus \mathcal{O}(0;1,1) \oplus \mathcal{O}(1;0,1)$

See the big table for more information.