Properties

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

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Invariants

Base field:  $\F_{7}$
Dimension:  $2$
L-polynomial:  $1 - x - 5 x^{2} - 7 x^{3} + 49 x^{4}$
Frobenius angles:  $\pm0.125193012804$, $\pm0.762660685111$
Angle rank:  $2$ (numerical)
Number field:  \(\Q(\sqrt{-34 +2 \sqrt{77}})\)
Galois group:  $D_{4}$
Jacobians:  $2$
Cyclic group of points:    yes

This isogeny class is simple and geometrically 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

$r$ $1$ $2$ $3$ $4$ $5$
$A(\F_{q^r})$ $37$ $1961$ $105931$ $6002621$ $280537552$

Point counts of the curve

$r$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$
$C(\F_{q^r})$ $7$ $39$ $307$ $2499$ $16692$ $118299$ $826105$ $5765043$ $40376881$ $282485854$

Jacobians and polarizations

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

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

Decomposition and endomorphism algebra

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

Endomorphism algebra over $\F_{7}$
The endomorphism algebra of this simple isogeny class is \(\Q(\sqrt{-34 +2 \sqrt{77}})\).

Base change

This is a primitive isogeny class.

Twists

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

TwistExtension degreeCommon base change
2.7.b_af$2$2.49.al_ef