Properties

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

Related objects

Downloads

Learn more

Invariants

Base field:  $\F_{5}$
Dimension:  $2$
L-polynomial:  $( 1 - 4 x + 5 x^{2} )( 1 + 4 x + 5 x^{2} )$
  $1 - 6 x^{2} + 25 x^{4}$
Frobenius angles:  $\pm0.147583617650$, $\pm0.852416382350$
Angle rank:  $1$ (numerical)
Jacobians:  $2$
Cyclic group of points:    no
Non-cyclic primes:   $2$

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

$r$ $1$ $2$ $3$ $4$ $5$
$A(\F_{q^r})$ $20$ $400$ $15860$ $409600$ $9766100$

Point counts of the curve

$r$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$
$C(\F_{q^r})$ $6$ $14$ $126$ $654$ $3126$ $16094$ $78126$ $392734$ $1953126$ $9766574$

Jacobians and polarizations

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

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

Decomposition and endomorphism algebra

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

Endomorphism algebra over $\F_{5}$
The isogeny class factors as 1.5.ae $\times$ 1.5.e and its endomorphism algebra is a direct product of the endomorphism algebras for each isotypic factor. The endomorphism algebra for each factor is:
Endomorphism algebra over $\overline{\F}_{5}$
The base change of $A$ to $\F_{5^{2}}$ is 1.25.ag 2 and its endomorphism algebra is $\mathrm{M}_{2}($\(\Q(\sqrt{-1}) \)$)$

Base change

This is a primitive isogeny class.

Twists

Below are some of the twists of this isogeny class.

TwistExtension degreeCommon base change
2.5.ai_ba$2$2.25.am_di
2.5.i_ba$2$2.25.am_di
2.5.ag_s$4$2.625.bc_cdq

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

TwistExtension degreeCommon base change
2.5.ai_ba$2$2.25.am_di
2.5.i_ba$2$2.25.am_di
2.5.ag_s$4$2.625.bc_cdq
2.5.ae_o$4$2.625.bc_cdq
2.5.ac_c$4$2.625.bc_cdq
2.5.a_g$4$2.625.bc_cdq
2.5.c_c$4$2.625.bc_cdq
2.5.e_o$4$2.625.bc_cdq
2.5.g_s$4$2.625.bc_cdq
2.5.ae_l$6$(not in LMFDB)
2.5.e_l$6$(not in LMFDB)
2.5.a_ai$8$(not in LMFDB)
2.5.a_i$8$(not in LMFDB)
2.5.ac_ab$12$(not in LMFDB)
2.5.c_ab$12$(not in LMFDB)