\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.

Lagrangian Grassmannian $\LGr(7,14)$

Y Z Y Z Y Z Y Z Y Z Y Z Y Z
Betti numbers
\begin{align*} \mathrm{b}_{ 0 } &= 1 \\ \mathrm{b}_{ 2 } &= 1 \\ \mathrm{b}_{ 4 } &= 1 \\ \mathrm{b}_{ 6 } &= 2 \\ \mathrm{b}_{ 8 } &= 2 \\ \mathrm{b}_{ 10 } &= 3 \\ \mathrm{b}_{ 12 } &= 4 \\ \mathrm{b}_{ 14 } &= 5 \\ \mathrm{b}_{ 16 } &= 5 \\ \mathrm{b}_{ 18 } &= 6 \\ \mathrm{b}_{ 20 } &= 7 \\ \mathrm{b}_{ 22 } &= 7 \\ \mathrm{b}_{ 24 } &= 8 \\ \mathrm{b}_{ 26 } &= 8 \\ \mathrm{b}_{ 28 } &= 8 \\ \mathrm{b}_{ 30 } &= 8 \\ \mathrm{b}_{ 32 } &= 8 \\ \mathrm{b}_{ 34 } &= 7 \\ \mathrm{b}_{ 36 } &= 7 \\ \mathrm{b}_{ 38 } &= 6 \\ \mathrm{b}_{ 40 } &= 5 \\ \mathrm{b}_{ 42 } &= 5 \\ \mathrm{b}_{ 44 } &= 4 \\ \mathrm{b}_{ 46 } &= 3 \\ \mathrm{b}_{ 48 } &= 2 \\ \mathrm{b}_{ 50 } &= 2 \\ \mathrm{b}_{ 52 } &= 1 \\ \mathrm{b}_{ 54 } &= 1 \\ \mathrm{b}_{ 56 } &= 1 \end{align*}
Basic information
dimension
28
index
8
Euler characteristic
128
Betti numbers
$\mathrm{b}_{ 0 } = 1$, $\mathrm{b}_{ 2 } = 1$, $\mathrm{b}_{ 4 } = 1$, $\mathrm{b}_{ 6 } = 2$, $\mathrm{b}_{ 8 } = 2$, $\mathrm{b}_{ 10 } = 3$, $\mathrm{b}_{ 12 } = 4$, $\mathrm{b}_{ 14 } = 5$, $\mathrm{b}_{ 16 } = 5$, $\mathrm{b}_{ 18 } = 6$, $\mathrm{b}_{ 20 } = 7$, $\mathrm{b}_{ 22 } = 7$, $\mathrm{b}_{ 24 } = 8$, $\mathrm{b}_{ 26 } = 8$, $\mathrm{b}_{ 28 } = 8$, $\mathrm{b}_{ 30 } = 8$, $\mathrm{b}_{ 32 } = 8$, $\mathrm{b}_{ 34 } = 7$, $\mathrm{b}_{ 36 } = 7$, $\mathrm{b}_{ 38 } = 6$, $\mathrm{b}_{ 40 } = 5$, $\mathrm{b}_{ 42 } = 5$, $\mathrm{b}_{ 44 } = 4$, $\mathrm{b}_{ 46 } = 3$, $\mathrm{b}_{ 48 } = 2$, $\mathrm{b}_{ 50 } = 2$, $\mathrm{b}_{ 52 } = 1$, $\mathrm{b}_{ 54 } = 1$, $\mathrm{b}_{ 56 } = 1$
$\mathrm{Aut}^0(\LGr(7,14))$
$\mathrm{PSp}_{ 14 }$
$\pi_0\mathrm{Aut}(\LGr(7,14))$
$1$
$\dim\mathrm{Aut}^0(\LGr(7,14))$
105
Projective geometry
minimal embedding

$\LGr(7,14)\hookrightarrow\mathbb{P}^{ 1429 }$

degree
48608795688960
Hilbert series
1, 1430, 379236, 37119160, 1844536720, 55804330152, 1153471856900, 17618122000050, 210309203300625, 2045253720802500, 16726481666902800, 117924492822177600, 731033150646450432, 4049210782061424320, 20306456189361772560, 93218107934594843356, 395354056003669808305, 1561373056164500587866, 5780818251270332339300, 20181961451776258981000, ...
Projective duality

The projective dual is a hypersurface.

codimension
1
degree
406247717856
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 $\mathbf D^{\mathrm b}(\LGr(7,14))$:

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 $\mathrm{c}_1(\LGr(7,14))$:

Homological projective duality

No Lefschetz decomposition recorded. Fullness of the Kuznetsov–Polishchuk collection does not give a Lefschetz decomposition. [Kuznetsov–Polishchuk] [Guseva–Novikov, Theorem 1.2]

No HP-dual model recorded.

$k$-Fanoness

2-Fano: $\mathrm{ch}_i(\mathrm{T}_{ \LGr(7,14) })\cdot Z>0$ 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. 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.
  2. Kuznetsov, Alexander; Polishchuk, Alexander. Exceptional collections on isotropic Grassmannians. J. Eur. Math. Soc. (JEMS) 18 (2016), 507–574. MR3463417.
  3. 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.
  4. Anton Fonarev. Full exceptional collections on Lagrangian Grassmannians. Int. Math. Res. Not. 2022 (2), 1081–1122. arXiv:1911.08968.
  5. 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.
  6. Lyalya Guseva; Alexander Novikov. Full exceptional collections on the symplectic isotropic Grassmannians. Advances in Mathematics (2026), article 111211. arXiv:2505.13005.
  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.