Properties

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

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Invariants

Base field:  $\F_{5}$
Dimension:  $2$
L-polynomial:  $1 + 7 x^{2} + 25 x^{4}$
Frobenius angles:  $\pm0.373408344447$, $\pm0.626591655553$
Angle rank:  $1$ (numerical)
Number field:  \(\Q(\sqrt{3}, \sqrt{-17})\)
Galois group:  $C_2^2$
Jacobians:  $3$
Isomorphism classes:  4
Cyclic group of points:    yes

This isogeny class is simple but not 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

$r$ $1$ $2$ $3$ $4$ $5$
$A(\F_{q^r})$ $33$ $1089$ $15444$ $393129$ $9761433$

Point counts of the curve

$r$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$
$C(\F_{q^r})$ $6$ $40$ $126$ $628$ $3126$ $15262$ $78126$ $393124$ $1953126$ $9757240$

Jacobians and polarizations

This isogeny class is principally polarizable and contains the Jacobians of 3 curves (of which all are hyperelliptic):

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

Decomposition and endomorphism algebra

All geometric endomorphisms are defined over $\F_{5^{2}}$.

Endomorphism algebra over $\F_{5}$
The endomorphism algebra of this simple isogeny class is \(\Q(\sqrt{3}, \sqrt{-17})\).
Endomorphism algebra over $\overline{\F}_{5}$
The base change of $A$ to $\F_{5^{2}}$ is 1.25.h 2 and its endomorphism algebra is $\mathrm{M}_{2}($\(\Q(\sqrt{-51}) \)$)$

Base change

This is a primitive isogeny class.

Twists

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

TwistExtension degreeCommon base change
2.5.a_ah$4$2.625.c_bwd
2.5.ad_i$12$(not in LMFDB)
2.5.d_i$12$(not in LMFDB)