\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.

Orthogonal Grassmannian $\OGr(4,15)$

Betti numbers
\begin{align*} \mathrm{b}_{ 1 } &= 1 \\ \mathrm{b}_{ 2 } &= 1 \\ \mathrm{b}_{ 3 } &= 2 \\ \mathrm{b}_{ 4 } &= 3 \\ \mathrm{b}_{ 5 } &= 5 \\ \mathrm{b}_{ 6 } &= 6 \\ \mathrm{b}_{ 7 } &= 9 \\ \mathrm{b}_{ 8 } &= 11 \\ \mathrm{b}_{ 9 } &= 14 \\ \mathrm{b}_{ 10 } &= 17 \\ \mathrm{b}_{ 11 } &= 20 \\ \mathrm{b}_{ 12 } &= 23 \\ \mathrm{b}_{ 13 } &= 26 \\ \mathrm{b}_{ 14 } &= 29 \\ \mathrm{b}_{ 15 } &= 30 \\ \mathrm{b}_{ 16 } &= 33 \\ \mathrm{b}_{ 17 } &= 33 \\ \mathrm{b}_{ 18 } &= 34 \\ \mathrm{b}_{ 19 } &= 33 \\ \mathrm{b}_{ 20 } &= 33 \\ \mathrm{b}_{ 21 } &= 30 \\ \mathrm{b}_{ 22 } &= 29 \\ \mathrm{b}_{ 23 } &= 26 \\ \mathrm{b}_{ 24 } &= 23 \\ \mathrm{b}_{ 25 } &= 20 \\ \mathrm{b}_{ 26 } &= 17 \\ \mathrm{b}_{ 27 } &= 14 \\ \mathrm{b}_{ 28 } &= 11 \\ \mathrm{b}_{ 29 } &= 9 \\ \mathrm{b}_{ 30 } &= 6 \\ \mathrm{b}_{ 31 } &= 5 \\ \mathrm{b}_{ 32 } &= 3 \\ \mathrm{b}_{ 33 } &= 2 \\ \mathrm{b}_{ 34 } &= 1 \\ \mathrm{b}_{ 35 } &= 1 \end{align*}
Basic information
dimension
34
index
10
Euler characteristic
560
Betti numbers
$\mathrm{b}_{ 1 } = 1$, $\mathrm{b}_{ 2 } = 1$, $\mathrm{b}_{ 3 } = 2$, $\mathrm{b}_{ 4 } = 3$, $\mathrm{b}_{ 5 } = 5$, $\mathrm{b}_{ 6 } = 6$, $\mathrm{b}_{ 7 } = 9$, $\mathrm{b}_{ 8 } = 11$, $\mathrm{b}_{ 9 } = 14$, $\mathrm{b}_{ 10 } = 17$, $\mathrm{b}_{ 11 } = 20$, $\mathrm{b}_{ 12 } = 23$, $\mathrm{b}_{ 13 } = 26$, $\mathrm{b}_{ 14 } = 29$, $\mathrm{b}_{ 15 } = 30$, $\mathrm{b}_{ 16 } = 33$, $\mathrm{b}_{ 17 } = 33$, $\mathrm{b}_{ 18 } = 34$, $\mathrm{b}_{ 19 } = 33$, $\mathrm{b}_{ 20 } = 33$, $\mathrm{b}_{ 21 } = 30$, $\mathrm{b}_{ 22 } = 29$, $\mathrm{b}_{ 23 } = 26$, $\mathrm{b}_{ 24 } = 23$, $\mathrm{b}_{ 25 } = 20$, $\mathrm{b}_{ 26 } = 17$, $\mathrm{b}_{ 27 } = 14$, $\mathrm{b}_{ 28 } = 11$, $\mathrm{b}_{ 29 } = 9$, $\mathrm{b}_{ 30 } = 6$, $\mathrm{b}_{ 31 } = 5$, $\mathrm{b}_{ 32 } = 3$, $\mathrm{b}_{ 33 } = 2$, $\mathrm{b}_{ 34 } = 1$, $\mathrm{b}_{ 35 } = 1$
$\mathrm{Aut}^0(\OGr(4,15))$
$\mathrm{SO}_{ 15 }$
$\pi_0\mathrm{Aut}(\OGr(4,15))$
$1$
$\dim\mathrm{Aut}^0(\OGr(4,15))$
105
Projective geometry
minimal embedding

$\OGr(4,15)\hookrightarrow\mathbb{P}^{ 1364 }$

degree
7980244599275520
Hilbert series
1, 1365, 433160, 55349280, 3718285560, 153867152439, 4352159136325, 90493971925500, 1458796644805500, 18980057629423800, 205630233149263104, 1901588329287362560, 15313281571069735680, 109158889795007479560, 698231388200772701340, 4053717515283316476596, 21569161178526095228325, 106058089955855157302875, 485395220136283311855000, 2080611984095705560500000, ...
Exceptional collections

No full exceptional collection is known for $\mathbf{D}^{\mathrm{b}}(\OGr(4,15))$. Will you be the first to construct one? Let us know if you do!

Kuznetsov–Polishchuk have constructed an exceptional collection of maximal length in MR3463417. Can you prove it's full?