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 $\rho$
$\rho(g_{1}) = \operatorname{diag}(1, \zeta_{3}, \zeta_{3}, 1)$
$\rho(g_{2}) = \operatorname{diag}(1, 1, 1, i)$
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 $\dim \mathrm{HH}^\bullet$
$(1, 2, 1, 4, 8, 4, 0, 0, 0)$
Hodge diamond
1
1 1
0 6 0
0 5 5 0
0 0 10 0 0
0 5 5 0
0 6 0
1 1
1
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
11
010
0220
02420
0220
000
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
060
0550
001000
0550
060
11
1
$\omega_X^{\otimes 1}$
0
00
020
0221
00411
0221
020
00
0
$\omega_X^{\otimes 2}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 3}$
0
10
110
0500
04400
0500
110
10
0
$\omega_X^{\otimes 4}$
0
20
221
0611
04420
0611
221
20
0
$\omega_X^{\otimes 5}$
0
00
002
0122
01140
0122
002
00
0
$\omega_X^{\otimes 6}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 7}$
0
00
200
2210
04110
2210
200
00
0
$\omega_X^{\otimes 8}$
0
02
122
1160
02440
1160
122
02
0
$\omega_X^{\otimes 9}$
0
01
011
0050
00440
0050
011
01
0
$\omega_X^{\otimes 10}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 11}$
0
00
020
1220
11400
1220
020
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