$\mathrm{S}_3 \times \mathrm{C}_2$ in dimension 4
This tangent representation satisfies the necessary conditions for a hyperelliptic fourfold, but it is not known whether it is realized by an actual variety. See completeness in dimension 4.
- holonomy group
- $\mathrm{S}_3 \times \mathrm{C}_2$, order $12$, SmallGroup $[12,4]$ · character table
- tangent representation $\rho$
- $\rho(g_{1}) = \operatorname{diag}(1, 1, 1, -1)$$\rho(g_{2}) = \operatorname{diag}(1, 1, -1, -1)$$\rho(g_{3}) = \operatorname{diag}(1, 1, \zeta_{3}, \zeta_{3}^{2})$$\rho \cong$ $2\,\chi_{ 1 }$ $\oplus$ $\chi_{ 6 }$
- order of $\omega_X$
- 2
- number of moduli
- 5
- irregularity $q = \dim \operatorname{Aut}^0(X)$
- 2
- Albanese
- the Albanese variety has dimension $2$; the general fiber has dimension $2$ and is an abelian variety or a hyperelliptic variety (details)
- $\mathbf{D}^{\mathrm{b}}(X)$
- indecomposable
- Hochschild cohomology $\dim \mathrm{HH}^\bullet$
- $(1, 4, 7, 8, 8, 8, 7, 4, 1)$
Hodge diamond
1
2 2
1 5 1
0 4 4 0
0 1 6 1 0
0 4 4 0
1 5 1
2 2
1
2 2
1 5 1
0 4 4 0
0 1 6 1 0
0 4 4 0
1 5 1
2 2
1
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
22
151
0440
01610
0440
151
22
1
22
151
0440
01610
0440
151
22
1
twisted Hodge numbers $\mathrm{h}^{p,q}(X,\omega_X^{\otimes j})$
Since $\operatorname{ord} \omega_X = 2$, the twists by powers of the canonical bundle form a finite package of $2$ diamonds (explained).
$\omega_X^{\otimes 0}$
1
22
151
0440
01610
0440
151
22
1
22
151
0440
01610
0440
151
22
1
$\omega_X^{\otimes 1}$
0
00
111
2442
15651
2442
111
00
0
00
111
2442
15651
2442
111
00
0
References
- A. Demleitner, The classification of hyperelliptic groups in dimension 4. arXiv:2211.07998
- A. Demleitner, C. Gleissner, The classification of rigid hyperelliptic fourfolds, Ann. Mat. Pura Appl. (4) 202 (2023) 1425–1450. MR4576947 doi
- P. Belmans, A. Demleitner, P. Núñez, The Albanese morphism for hyperelliptic varieties, Indag. Math. (N.S.) 37 (2026) 1450–1475. MR5103244 doi