Abelian variety isogeny class 2.7.c_ab over $\F_{7}$

• Label: 2.7.c_ab
• Base field: $\F_{7}$
• Dimension: $2$
• $p$-rank: $2$
• Ordinary: yes
• Supersingular: no
• Simple: no
• Geometrically simple: no
• Primitive: yes
• Principally polarizable: yes
• Contains a Jacobian: yes

Invariants

Base field:	$\F_{7}$
Dimension:	$2$
L-polynomial:	$( 1 - 3 x + 7 x^{2} )( 1 + 5 x + 7 x^{2} )$
	$1 + 2 x - x^{2} + 14 x^{3} + 49 x^{4}$
Frobenius angles:	$\pm0.308124534521$, $\pm0.893852192495$
Angle rank:	$2$ (numerical)
Jacobians:	$4$
Isomorphism classes:	12

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

Newton polygon

This isogeny class is ordinary.

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

Point counts

Point counts of the abelian variety

$r$	$1$	$2$	$3$	$4$	$5$
$A(\F_{q^r})$	$65$	$2145$	$138320$	$5888025$	$281534825$

Point counts of the curve

$r$	$1$	$2$	$3$	$4$	$5$	$6$	$7$	$8$	$9$	$10$
$C(\F_{q^r})$	$10$	$44$	$400$	$2452$	$16750$	$117326$	$820690$	$5768548$	$40350640$	$282540764$

Jacobians and polarizations

This isogeny class is principally polarizable and contains the Jacobians of 4 curves (of which all are hyperelliptic):

• $y^2=4 x^6+3 x^5+5 x^4+3 x^3+x+6$
• $y^2=2 x^6+2 x^5+3 x^4+5 x^3+5 x^2+3$
• $y^2=4 x^6+5 x^5+x^4+6 x^3+x^2+5 x+4$
• $y^2=4 x^6+2 x^5+5 x^4+6 x^3+x+1$

Decomposition and endomorphism algebra

All geometric endomorphisms are defined over $\F_{7}$.

Endomorphism algebra over $\F_{7}$

The isogeny class factors as 1.7.ad $\times$ 1.7.f and its endomorphism algebra is a direct product of the endomorphism algebras for each isotypic factor. The endomorphism algebra for each factor is:

• 1.7.ad : \(\Q(\sqrt{-19}) \).
• 1.7.f : \(\Q(\sqrt{-3}) \).

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
2.7.ai_bd	$2$	2.49.ag_br
2.7.ac_ab	$2$	2.49.ag_br
2.7.i_bd	$2$	2.49.ag_br
2.7.ah_ba	$3$	2.343.ce_ccc
2.7.ae_r	$3$	2.343.ce_ccc