Properties

Label 2.7.ab_ad
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:  $1 - x - 3 x^{2} - 7 x^{3} + 49 x^{4}$
Frobenius angles:  $\pm0.157948536279$, $\pm0.742570314434$
Angle rank:  $2$ (numerical)
Number field:  \(\Q(\sqrt{-42 +2 \sqrt{69}})\)
Galois group:  $D_{4}$
Jacobians:  $4$
Isomorphism classes:  4
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

$r$ $1$ $2$ $3$ $4$ $5$
$A(\F_{q^r})$ $39$ $2145$ $107757$ $6102525$ $283215504$

Point counts of the curve

$r$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$
$C(\F_{q^r})$ $7$ $43$ $313$ $2539$ $16852$ $118231$ $826735$ $5763331$ $40363621$ $282474718$

Jacobians and polarizations

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

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

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 \(\Q(\sqrt{-42 +2 \sqrt{69}})\).

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_ad$2$2.49.ah_dp