hyperelliptic(.ncag).info

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

$\mathrm{S}_3 \times \mathrm{C}_4$ 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
$\mathrm{S}_3 \times \mathrm{C}_4$, order $24$, SmallGroup $[24,5]$ · character table
tangent representation $\rho$
$\rho(g_{1}) = \operatorname{diag}(1, -1, -1, -1)$
$\rho(g_{2}) = \operatorname{diag}(1, -1, -1, -i)$
$\rho(g_{3}) = \operatorname{diag}(1, 1, 1, -1)$
$\rho(g_{4}) = \operatorname{diag}(1, 1, \zeta_{3}, \zeta_{3}^{2})$
$\rho \cong$ $\chi_{ 3 }$ $\oplus$ $\chi_{ 6 }$ $\oplus$ $\chi_{ 10 }$
order of $\omega_X$
4
number of moduli
2
irregularity $q = \dim \operatorname{Aut}^0(X)$
0
Albanese
the Albanese variety is a point; the fiber is $X$ itself (details)
$\mathbf{D}^{\mathrm{b}}(X)$
indecomposability open (why)
Hochschild cohomology $\dim \mathrm{HH}^\bullet$
$(1, 0, 2, 6, 2, 0, 1, 0, 0)$
Hodge diamond
1
0 0
0 3 0
1 2 2 1
0 0 4 0 0
1 2 2 1
0 3 0
0 0
1
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
00
020
1221
00200
0000
010
00
0

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

Since $\operatorname{ord} \omega_X = 4$, the twists by powers of the canonical bundle form a finite package of $4$ diamonds (explained).

$\omega_X^{\otimes 0}$
1
00
030
1221
00400
1221
030
00
1
$\omega_X^{\otimes 1}$
0
01
000
0020
01221
0020
000
01
0
$\omega_X^{\otimes 2}$
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 3}$
0
10
000
0200
12210
0200
000
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