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

• Label: 4.2.af_o_abc_bs
• Base field: $\F_{2}$
• Dimension: $4$
• $p$-rank: $1$
• 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:	$( 1 - 2 x + 2 x^{2} )( 1 - x + 2 x^{2} )( 1 - 2 x + 2 x^{2} - 4 x^{3} + 4 x^{4} )$
	$1 - 5 x + 14 x^{2} - 28 x^{3} + 44 x^{4} - 56 x^{5} + 56 x^{6} - 40 x^{7} + 16 x^{8}$
Frobenius angles:	$\pm0.0833333333333$, $\pm0.250000000000$, $\pm0.384973271919$, $\pm0.583333333333$
Angle rank:	$1$ (numerical)
Jacobians:	$0$
Isomorphism classes:	10

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

Newton polygon

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

Point counts

Point counts of the abelian variety

$r$	$1$	$2$	$3$	$4$	$5$
$A(\F_{q^r})$	$2$	$520$	$4550$	$67600$	$1191542$

Point counts of the (virtual) curve

$r$	$1$	$2$	$3$	$4$	$5$	$6$	$7$	$8$	$9$	$10$
$C(\F_{q^r})$	$-2$	$8$	$10$	$16$	$38$	$56$	$110$	$288$	$550$	$968$

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 $\F_{2^{12}}$.

Endomorphism algebra over $\F_{2}$

The isogeny class factors as 1.2.ac $\times$ 1.2.ab $\times$ 2.2.ac_c 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 : \(\Q(\sqrt{-1}) \).
• 1.2.ab : \(\Q(\sqrt{-7}) \).
• 2.2.ac_c : \(\Q(\zeta_{12})\).

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

The base change of $A$ to $\F_{2^{12}}$ is 1.4096.bv $\times$ 1.4096.ey^3. The endomorphism algebra for each factor is:

• 1.4096.bv : \(\Q(\sqrt{-7}) \).
• 1.4096.ey^3 : $\mathrm{M}_{3}(B)$, where $B$ is the quaternion algebra over \(\Q\) ramified at $2$ and $\infty$.

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 $\times$ 1.4.d $\times$ 2.4.a_ae. The endomorphism algebra for each factor is:

  • 1.4.a : \(\Q(\sqrt{-1}) \).
  • 1.4.d : \(\Q(\sqrt{-7}) \).
  • 2.4.a_ae : \(\Q(\zeta_{12})\).
• Endomorphism algebra over $\F_{2^{3}}$
  The base change of $A$ to $\F_{2^{3}}$ is 1.8.ae^2 $\times$ 1.8.e $\times$ 1.8.f. The endomorphism algebra for each factor is:

  • 1.8.ae^2 : $\mathrm{M}_{2}($\(\Q(\sqrt{-1}) \)$)$
  • 1.8.e : \(\Q(\sqrt{-1}) \).
  • 1.8.f : \(\Q(\sqrt{-7}) \).
• Endomorphism algebra over $\F_{2^{4}}$
  The base change of $A$ to $\F_{2^{4}}$ is 1.16.ae^2 $\times$ 1.16.ab $\times$ 1.16.i. The endomorphism algebra for each factor is:

  • 1.16.ae^2 : $\mathrm{M}_{2}($\(\Q(\sqrt{-3}) \)$)$
  • 1.16.ab : \(\Q(\sqrt{-7}) \).
  • 1.16.i : the quaternion algebra over \(\Q\) ramified at $2$ and $\infty$.
• Endomorphism algebra over $\F_{2^{6}}$
  The base change of $A$ to $\F_{2^{6}}$ is 1.64.aj $\times$ 1.64.a^3. The endomorphism algebra for each factor is:

  • 1.64.aj : \(\Q(\sqrt{-7}) \).
  • 1.64.a^3 : $\mathrm{M}_{3}($\(\Q(\sqrt{-1}) \)$)$

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_g_am_u	$2$	4.4.d_e_a_a
4.2.ab_c_ae_e	$2$	4.4.d_e_a_a
4.2.ab_c_e_ae	$2$	4.4.d_e_a_a
4.2.b_c_ae_ae	$2$	4.4.d_e_a_a
4.2.b_c_e_e	$2$	4.4.d_e_a_a
4.2.d_g_m_u	$2$	4.4.d_e_a_a
4.2.f_o_bc_bs	$2$	4.4.d_e_a_a
4.2.b_c_c_i	$3$	(not in LMFDB)