$\mathrm{C}_{12}$ 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
- $\mathrm{C}_{12}$, order $12$, SmallGroup $[12,2]$ · character table
- tangent representation $\rho$
- $\rho(g_{1}) = \operatorname{diag}(1, \zeta_{3}, 1, \zeta_{3})$$\rho(g_{2}) = \operatorname{diag}(1, 1, i, -1)$
- order of $\omega_X$
- 12
- number of moduli
- 1
- irregularity $q = \dim \operatorname{Aut}^0(X)$
- 1
- Albanese
- the Albanese variety has dimension $1$; the general fiber has dimension $3$ and is an abelian variety or a hyperelliptic variety (details)
- $\mathbf{D}^{\mathrm{b}}(X)$
- indecomposable
- Hochschild cohomology $\dim \mathrm{HH}^\bullet$
- $(1, 2, 1, 2, 4, 4, 4, 2, 0)$
Hodge diamond
1
1 1
0 4 0
0 3 3 0
0 0 6 0 0
0 3 3 0
0 4 0
1 1
1
1 1
0 4 0
0 3 3 0
0 0 6 0 0
0 3 3 0
0 4 0
1 1
1
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
11
010
0110
01210
0220
121
11
0
11
010
0110
01210
0220
121
11
0
twisted Hodge numbers $\mathrm{h}^{p,q}(X,\omega_X^{\otimes j})$
Since $\operatorname{ord} \omega_X = 12$, the twists by powers of the canonical bundle form a finite package of $12$ diamonds (explained).
$\omega_X^{\otimes 0}$
1
11
040
0330
00600
0330
040
11
1
11
040
0330
00600
0330
040
11
1
$\omega_X^{\otimes 1}$
0
00
110
1211
02211
1211
110
00
0
00
110
1211
02211
1211
110
00
0
$\omega_X^{\otimes 2}$
0
01
111
1130
02220
1130
111
01
0
01
111
1130
02220
1130
111
01
0
$\omega_X^{\otimes 3}$
0
01
011
0230
02420
0230
011
01
0
01
011
0230
02420
0230
011
01
0
$\omega_X^{\otimes 4}$
0
10
110
0300
02200
0300
110
10
0
10
110
0300
02200
0300
110
10
0
$\omega_X^{\otimes 5}$
0
00
011
0221
01320
0221
011
00
0
00
011
0221
01320
0221
011
00
0
$\omega_X^{\otimes 6}$
0
00
020
0220
00400
0220
020
00
0
00
020
0220
00400
0220
020
00
0
$\omega_X^{\otimes 7}$
0
00
110
1220
02310
1220
110
00
0
00
110
1220
02310
1220
110
00
0
$\omega_X^{\otimes 8}$
0
01
011
0030
00220
0030
011
01
0
01
011
0030
00220
0030
011
01
0
$\omega_X^{\otimes 9}$
0
10
110
0320
02420
0320
110
10
0
10
110
0320
02420
0320
110
10
0
$\omega_X^{\otimes 10}$
0
10
111
0311
02220
0311
111
10
0
10
111
0311
02220
0311
111
10
0
$\omega_X^{\otimes 11}$
0
00
011
1121
11220
1121
011
00
0
00
011
1121
11220
1121
011
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