hyperelliptic(.ncag).info

the classification of hyperelliptic varieties in dimensions 2, 3 and 4

$\mathrm{C}_{12}$ 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 $\rho$
$\rho(g_{1}) = \operatorname{diag}(1, 1, \zeta_{3}, \zeta_{3})$
$\rho(g_{2}) = \operatorname{diag}(1, i, i, -i)$
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 $\dim \mathrm{HH}^\bullet$
$(1, 2, 1, 0, 4, 8, 4, 0, 0)$
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
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
11
010
0000
01210
1331
121
00
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
$\omega_X^{\otimes 1}$
0
10
110
0301
02211
0301
110
10
0
$\omega_X^{\otimes 2}$
0
00
011
0121
00220
0121
011
00
0
$\omega_X^{\otimes 3}$
0
10
110
0320
02420
0320
110
10
0
$\omega_X^{\otimes 4}$
0
00
111
1221
02220
1221
111
00
0
$\omega_X^{\otimes 5}$
0
01
011
0130
01320
0130
011
01
0
$\omega_X^{\otimes 6}$
0
00
020
0220
00400
0220
020
00
0
$\omega_X^{\otimes 7}$
0
10
110
0310
02310
0310
110
10
0
$\omega_X^{\otimes 8}$
0
00
111
1221
02220
1221
111
00
0
$\omega_X^{\otimes 9}$
0
01
011
0230
02420
0230
011
01
0
$\omega_X^{\otimes 10}$
0
00
110
1210
02200
1210
110
00
0
$\omega_X^{\otimes 11}$
0
01
011
1030
11220
1030
011
01
0

References

  1. A. Demleitner, The classification of hyperelliptic groups in dimension 4. arXiv:2211.07998
  2. A. Demleitner, C. Gleissner, The classification of rigid hyperelliptic fourfolds, Ann. Mat. Pura Appl. (4) 202 (2023) 1425–1450. MR4576947 doi
  3. P. Belmans, A. Demleitner, P. Núñez, The Albanese morphism for hyperelliptic varieties, Indag. Math. (N.S.) 37 (2026) 1450–1475. MR5103244 doi