Fanography

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

Identification

Fano variety 1-7

section of Plücker embedding of $\mathrm{Gr}(2,6)$ by codimension 5 subspace

Picard rank
1 (others)
$-\mathrm{K}_X^3$
14
$\mathrm{h}^{1,2}(X)$
5
Mori–Mukai $d$
14
Hodge diamond and polyvector parallelogram
1
0 0
0 1 0
0 5 5 0
0 1 0
0 0
1
1
0 0
0 15 0
0 0 0 10
0 0 0
0 0
0
Poisson structures

No nontrivial holomorphic Poisson structures.

See Loray–Pereira–Touzet.

Anticanonical bundle
index
1
$\dim\mathrm{H}^0(X,\omega_X^\vee)$
10
$-\mathrm{K}_X$ very ample?
yes
$-\mathrm{K}_X$ basepoint free?
yes
hyperelliptic
no
trigonal
no
Birational geometry

This variety is not rational but unirational.

A very general member is not stably rational.

The Weyl group associated to the KKMR decomposition is $\{e\}$; see the Weyl-group table for sources and conventions.


This variety is primitive.


This variety is fibre-like, i.e. it can appear as the fibre of a Mori fibre space.

Deformation theory
number of moduli
15
Bott vanishing
does not hold
$\mathrm{Aut}^0(X)$$\dim\mathrm{Aut}^0(X)$number of moduli
$0$015
Period sequence

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

GRDB
#147
Fanosearch
#18
Semiorthogonal decompositions

The naive atomic decomposition has atom dimensions $2+1+1$.

A standard semiorthogonal decomposition is $\langle \operatorname{Ku}(X), \mathcal{E}_2, \mathcal{O}_X \rangle$.

Both decompositions are recorded in Böhning–Graf von Bothmer–Su'a.

Structure of quantum cohomology

By Hertling–Manin–Teleman we have that quantum cohomology cannot be generically semisimple, as $\mathrm{h}^{1,2}\neq 0$.

Zero section description

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

variety
$\operatorname{Gr}(2,6)$
bundle
$\mathcal{O}(1)^{\oplus5}$

See the big table for more information.

K-stability
  • every member is K‑stable
  • every member is K‑polystable
  • every member is K‑semistable
Seeand the big table for more information.
Coregularity

For this deformation family, the general member has coregularity 0.

The generic and uniform statements are due to Avilov–Loginov–Przyjalkowski; the existence of a smooth member of coregularity zero in every family is due to Zhakupov.

See coregularity for terminology.

Futaki invariant

For every K-polystable member, the Futaki invariant vanishes identically on the entire Kähler cone.

This is the computation of Sektnan–Tipler.

Hilbert schemes of curves

The Hilbert scheme of conics is a Fano surface, a minimal surface of general type.

Its Hodge diamond is

1
5 5
10 25 10
5 5
1