\begin{equation} \DeclareMathOperator\Gr{Gr} \DeclareMathOperator\LGr{LGr} \DeclareMathOperator\OGr{OGr} \DeclareMathOperator\SGr{SGr} \DeclareMathOperator\Kzero{K_0} \DeclareMathOperator\index{i} \DeclareMathOperator\rk{rk} \end{equation}

Grassmannian.info

A periodic table of (generalised) Grassmannians.

Grassmannian $\Gr(4,7)$

There exist other realisations of this Grassmannian:
Betti numbers
\begin{align*} \mathrm{b}_{ 0 } &= 1 \\ \mathrm{b}_{ 2 } &= 1 \\ \mathrm{b}_{ 4 } &= 2 \\ \mathrm{b}_{ 6 } &= 3 \\ \mathrm{b}_{ 8 } &= 4 \\ \mathrm{b}_{ 10 } &= 4 \\ \mathrm{b}_{ 12 } &= 5 \\ \mathrm{b}_{ 14 } &= 4 \\ \mathrm{b}_{ 16 } &= 4 \\ \mathrm{b}_{ 18 } &= 3 \\ \mathrm{b}_{ 20 } &= 2 \\ \mathrm{b}_{ 22 } &= 1 \\ \mathrm{b}_{ 24 } &= 1 \end{align*}
Basic information
dimension
12
index
7
Euler characteristic
35
Betti numbers
$\mathrm{b}_{ 0 } = 1$, $\mathrm{b}_{ 2 } = 1$, $\mathrm{b}_{ 4 } = 2$, $\mathrm{b}_{ 6 } = 3$, $\mathrm{b}_{ 8 } = 4$, $\mathrm{b}_{ 10 } = 4$, $\mathrm{b}_{ 12 } = 5$, $\mathrm{b}_{ 14 } = 4$, $\mathrm{b}_{ 16 } = 4$, $\mathrm{b}_{ 18 } = 3$, $\mathrm{b}_{ 20 } = 2$, $\mathrm{b}_{ 22 } = 1$, $\mathrm{b}_{ 24 } = 1$
$\mathrm{Aut}^0(\Gr(4,7))$
$\mathrm{PGL}_{ 7 }$
$\pi_0\mathrm{Aut}(\Gr(4,7))$
$1$
$\dim\mathrm{Aut}^0(\Gr(4,7))$
48
Projective geometry
minimal embedding

$\Gr(4,7)\hookrightarrow\mathbb{P}^{ 34 }$

degree
462
Hilbert series
1, 35, 490, 4116, 24696, 116424, 457380, 1557270, 4723719, 13026013, 33157124, 78835120, 176729280, 376375104, 766192176, 1498581756, 2828205765, 5168991135, 9177226366, 15870391460, ...
Projective duality

The projective dual is a hypersurface.

codimension
1
degree
7
self-dual
no

[Tevelev, Theorems 9.19 and 10.22 (arXiv version)] [Tevelev, Theorems 7.1–7.2 (arXiv version)] All Grassmannians.

Exceptional collections

Full exceptional collections in $\mathbf D^{\mathrm b}(\Gr(4,7))$:

Quantum cohomology
small
generically semisimple [Chaput–Manivel–Perrin]

Minuscule/cominuscule case, including quadric realisations.

big
generically semisimple [Li–Liu–Yu–Zhang, Theorems 1.2 and 1.4]

Convergent near the large-radius limit.

Eigenvalues of quantum multiplication by $\mathrm{c}_1(\Gr(4,7))$:

Homological projective duality

Full minimal rectangular Lefschetz collection. [Fonarev (Lefschetz), Theorem 4.1 and Proposition 4.8]

Lefschetz block sizes: 5, 5, 5, 5, 5, 5, 5

Block sizes $(5, 5, 5, 5, 5, 5, 5)$; 35 objects.

Schur functors indexed by upper-triangular Young diagrams.

HP dual: matrix factorizations on a noncommutative crepant resolution, for Fonarev's rectangular decomposition. [Doyle, Theorem 5.13 (coprime case)]

$k$-Fanoness

2-Fano: $\mathrm{ch}_i(\mathrm{T}_{ \Gr(4,7) })\cdot Z>0$ for every nonzero effective $i$-dimensional cycle $Z$ and $1\leq i\leq 2$. [Araujo et al., Theorems 1.3 and 1.4]

References
  1. Kapranov, M. M. On the derived categories of coherent sheaves on some homogeneous spaces. Invent. Math. 92 (1988), 479–508. MR939472.
  2. Pierre-Emmanuel Chaput; Laurent Manivel; Nicolas Perrin. Quantum cohomology of minuscule homogeneous spaces III : semi-simplicity and consequences. Canad. J. Math. 62 (2010), 1246–1263. arXiv:0710.1224.
  3. Anton Fonarev. On minimal Lefschetz decompositions for Grassmannians. Izv. Math. 77 (2013), 1044–1065. arXiv:1108.2292.
  4. Bradley Doyle. Homological Projective Duality for the Plücker embedding of the Grassmannian. Preprint (2021). arXiv:2110.10589.
  5. Carolina Araujo; Roya Beheshti; Ana-Maria Castravet; Kelly Jabbusch; Svetlana Makarova; Enrica Mazzon; Libby Taylor; Nivedita Viswanathan. Higher Fano Manifolds. Rev. Un. Mat. Argentina 64 (2022), 103–125. arXiv:2110.02339.
  6. Alexander Samokhin; Wilberd van der Kallen. Highest weight category structures on $\operatorname{rep}(B)$ and full exceptional collections on generalized flag varieties over $\mathbb Z$. Preprint (2024). arXiv:2407.13653.
  7. Changzheng Li; Zhaoyang Liu; Tony Yue Yu; Chi Zhang. Convergence and semisimplicity of big quantum cohomology of flag varieties. Preprint (2026). arXiv:2610.28418.

All references.