Abelian variety isogeny class 4.2.af_p_abe_bw over $\F_{2}$

• Label: 4.2.af_p_abe_bw
• Base field: $\F_{2}$
• Dimension: $4$
• $p$-rank: $2$
• Ordinary: no
• Supersingular: no
• Simple: no
• Geometrically simple: no
• Primitive: yes
• Principally polarizable: yes
• Contains a Jacobian: no

Invariants

Base field:	$\F_{2}$
Dimension:	$4$
L-polynomial:	$( 1 - 2 x + 2 x^{2} )^{2}( 1 - x + 3 x^{2} - 2 x^{3} + 4 x^{4} )$
	$1 - 5 x + 15 x^{2} - 30 x^{3} + 48 x^{4} - 60 x^{5} + 60 x^{6} - 40 x^{7} + 16 x^{8}$
Frobenius angles:	$\pm0.250000000000$, $\pm0.250000000000$, $\pm0.306143893905$, $\pm0.570118980449$
Angle rank:	$2$ (numerical)
Jacobians:	$0$

This isogeny class is not simple, primitive, not ordinary, and not supersingular. It is principally polarizable.

Newton polygon

$p$-rank:	$2$
Slopes:	$[0, 0, 1/2, 1/2, 1/2, 1/2, 1, 1]$

Point counts

Point counts of the abelian variety

$r$	$1$	$2$	$3$	$4$	$5$
$A(\F_{q^r})$	$5$	$1375$	$13520$	$171875$	$2311375$

Point counts of the (virtual) curve

$r$	$1$	$2$	$3$	$4$	$5$	$6$	$7$	$8$	$9$	$10$
$C(\F_{q^r})$	$-2$	$10$	$19$	$34$	$58$	$55$	$54$	$194$	$523$	$1050$

Jacobians and polarizations

This isogeny class is principally polarizable, but does not contain a Jacobian.

Decomposition and endomorphism algebra

All geometric endomorphisms are defined over $\F_{2^{4}}$.

Endomorphism algebra over $\F_{2}$

The isogeny class factors as 1.2.ac^2 $\times$ 2.2.ab_d and its endomorphism algebra is a direct product of the endomorphism algebras for each isotypic factor. The endomorphism algebra for each factor is:

• 1.2.ac^2 : $\mathrm{M}_{2}($\(\Q(\sqrt{-1}) \)$)$
• 2.2.ab_d : 4.0.1025.1.

Endomorphism algebra over $\overline{\F}_{2}$

The base change of $A$ to $\F_{2^{4}}$ is 1.16.i^2 $\times$ 2.16.b_b. The endomorphism algebra for each factor is:

• 1.16.i^2 : $\mathrm{M}_{2}(B)$, where $B$ is the quaternion algebra over \(\Q\) ramified at $2$ and $\infty$.
• 2.16.b_b : 4.0.1025.1.

Remainder of endomorphism lattice by field

• Endomorphism algebra over $\F_{2^{2}}$
  The base change of $A$ to $\F_{2^{2}}$ is 1.4.a^2 $\times$ 2.4.f_n. The endomorphism algebra for each factor is:

  • 1.4.a^2 : $\mathrm{M}_{2}($\(\Q(\sqrt{-1}) \)$)$
  • 2.4.f_n : 4.0.1025.1.

Base change

This is a primitive isogeny class.

Twists

Below are some of the twists of this isogeny class.

Twist	Extension degree	Common base change
4.2.ad_h_ak_q	$2$	4.4.f_v_ci_fg
4.2.ab_d_ac_i	$2$	4.4.f_v_ci_fg
4.2.b_d_c_i	$2$	4.4.f_v_ci_fg
4.2.d_h_k_q	$2$	4.4.f_v_ci_fg
4.2.f_p_be_bw	$2$	4.4.f_v_ci_fg
4.2.b_d_g_g	$3$	(not in LMFDB)