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 $\rho$
$\rho(g_{1}) = \operatorname{diag}(1, \zeta_{3}, 1, \zeta_{3})$
$\rho(g_{2}) = \operatorname{diag}(1, 1, i, -1)$
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
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
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
$\omega_X^{\otimes 1}$
0
00
110
1211
02211
1211
110
00
0
$\omega_X^{\otimes 2}$
0
01
111
1130
02220
1130
111
01
0
$\omega_X^{\otimes 3}$
0
01
011
0230
02420
0230
011
01
0
$\omega_X^{\otimes 4}$
0
10
110
0300
02200
0300
110
10
0
$\omega_X^{\otimes 5}$
0
00
011
0221
01320
0221
011
00
0
$\omega_X^{\otimes 6}$
0
00
020
0220
00400
0220
020
00
0
$\omega_X^{\otimes 7}$
0
00
110
1220
02310
1220
110
00
0
$\omega_X^{\otimes 8}$
0
01
011
0030
00220
0030
011
01
0
$\omega_X^{\otimes 9}$
0
10
110
0320
02420
0320
110
10
0
$\omega_X^{\otimes 10}$
0
10
111
0311
02220
0311
111
10
0
$\omega_X^{\otimes 11}$
0
00
011
1121
11220
1121
011
00
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