Fanography

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

Identification

Fano variety 5-2

blowup of 3-25 in the disjoint union of two exceptional lines on the same irreducible component

Picard rank
5 (others)
$-\mathrm{K}_X^3$
36
$\mathrm{h}^{1,2}(X)$
0
Hodge diamond
1
0 0
0 5 0
0 0 0 0
0 5 0
0 0
1
1
0 5
0 0 13
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

  • 4-9, in a curve of genus 0
  • 4-11, in a curve of genus 0
  • 4-12, in a curve of genus 0
Deformation theory
number of moduli
0

$\mathrm{Aut}^0(X)$ $\dim\mathrm{Aut}^0(X)$ number of moduli
$\mathbb{G}_{\mathrm{m}}\times\mathrm{GL}_2$ 5 0
Period sequence

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

GRDB
#64
Fanosearch
#87
Extremal contractions
Semiorthogonal decompositions

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

Alternatively, Kawamata has constructed a full exceptional collection for every smooth projective toric variety.

Structure of quantum cohomology

Generic semisimplicity of:

  • small quantum cohomology, proved by Iritani in 2007, see [MR2359850] , using toric geometry
Zero section description

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

variety
$\mathbb{P}^1 \times \mathbb{P}^3 \times \mathbb{P}^{8} \times \mathbb{P}^1$
bundle
$\mathcal{O}(1,1,0,0) \oplus \Lambda(0,0,1,0) \oplus \mathcal{O}(-1,1,1,0) \oplus \mathcal{O}(0,1,0,1)$

See the big table for more information.

Toric geometry

This variety is toric.

It corresponds to ID #15 on grdb.co.uk.