Abelian variety isogeny class 2.5.ac_a over $\F_{5}$

• Label: 2.5.ac_a
• Base field: $\F_{5}$
• Dimension: $2$
• $p$-rank: $1$
• Ordinary: no
• Supersingular: no
• Simple: yes
• Geometrically simple: yes
• Primitive: yes
• Principally polarizable: yes
• Contains a Jacobian: yes

Invariants

Base field:	$\F_{5}$
Dimension:	$2$
L-polynomial:	$1 - 2 x - 10 x^{3} + 25 x^{4}$
Frobenius angles:	$\pm0.0841889326552$, $\pm0.673328138963$
Angle rank:	$2$ (numerical)
Number field:	4.0.38720.3
Galois group:	$D_{4}$
Jacobians:	$2$
Isomorphism classes:	2

This isogeny class is simple and geometrically simple, primitive, not ordinary, and not supersingular. It is principally polarizable and contains a Jacobian.

Newton polygon

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

Point counts

Point counts of the abelian variety

$r$	$1$	$2$	$3$	$4$	$5$
$A(\F_{q^r})$	$14$	$532$	$11438$	$393680$	$9826894$

Point counts of the curve

$r$	$1$	$2$	$3$	$4$	$5$	$6$	$7$	$8$	$9$	$10$
$C(\F_{q^r})$	$4$	$22$	$88$	$630$	$3144$	$15382$	$78628$	$391710$	$1952404$	$9775302$

Jacobians and polarizations

This isogeny class contains the Jacobians of 2 curves (of which all are hyperelliptic), and hence is principally polarizable:

• $y^2=3x^6+4x^4+4x^2+2x+2$
• $y^2=2x^6+3x^5+2x^4+4x^3+4x+3$

Decomposition and endomorphism algebra

All geometric endomorphisms are defined over $\F_{5}$.

Endomorphism algebra over $\F_{5}$

The endomorphism algebra of this simple isogeny class is 4.0.38720.3.

Base change

This is a primitive isogeny class.

Twists

Below is a list of all twists of this isogeny class.

Twist	Extension degree	Common base change
2.5.c_a	$2$	2.25.ae_k