hyperelliptic(.ncag).info

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

$\mathrm{C}_{6}$ 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
$\mathrm{C}_{6}$, order $6$, SmallGroup $[6,2]$ · character table
tangent representation $\rho$
$\rho(g_{1}) = \operatorname{diag}(1, 1, 1, -1)$
$\rho(g_{2}) = \operatorname{diag}(1, 1, 1, \zeta_{3})$
order of $\omega_X$
6
number of moduli
9
irregularity $q = \dim \operatorname{Aut}^0(X)$
3
Albanese
the Albanese variety has dimension $3$; the general fiber has dimension $1$ and is an elliptic curve (details)
$\mathbf{D}^{\mathrm{b}}(X)$
indecomposable
Hochschild cohomology $\dim \mathrm{HH}^\bullet$
$(1, 6, 15, 20, 15, 6, 1, 0, 0)$
Hodge diamond
1
3 3
3 10 3
1 12 12 1
0 6 18 6 0
1 12 12 1
3 10 3
3 3
1
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
33
393
1991
03930
0330
010
00
0

twisted Hodge numbers $\mathrm{h}^{p,q}(X,\omega_X^{\otimes j})$

Since $\operatorname{ord} \omega_X = 6$, the twists by powers of the canonical bundle form a finite package of $6$ diamonds (explained).

$\omega_X^{\otimes 0}$
1
33
3103
112121
061860
112121
3103
33
1
$\omega_X^{\otimes 1}$
0
01
033
0393
01991
0393
033
01
0
$\omega_X^{\otimes 2}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 3}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 4}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 5}$
0
10
330
3930
19910
3930
330
10
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