Properties

Label 2.41.a_c
Base field $\F_{41}$
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:  $\F_{41}$
Dimension:  $2$
L-polynomial:  $1 + 2 x^{2} + 1681 x^{4}$
Frobenius angles:  $\pm0.253882212856$, $\pm0.746117787144$
Angle rank:  $1$ (numerical)
Number field:  \(\Q(\sqrt{5}, \sqrt{-21})\)
Galois group:  $C_2^2$
Jacobians:  $212$
Cyclic group of points:    no
Non-cyclic primes:   $2$

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

$r$ $1$ $2$ $3$ $4$ $5$
$A(\F_{q^r})$ $1684$ $2835856$ $4750094164$ $8003919974400$ $13422659338342804$

Point counts of the curve

$r$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$
$C(\F_{q^r})$ $42$ $1686$ $68922$ $2832478$ $115856202$ $4750084086$ $194754273882$ $7984913979838$ $327381934393962$ $13422659366533206$

Jacobians and polarizations

This isogeny class is principally polarizable and contains the Jacobians of 212 curves (of which all are hyperelliptic):

  • $y^2=10 x^6+5 x^5+23 x^4+29 x^3+36 x^2+38 x+36$
  • $y^2=19 x^6+30 x^5+15 x^4+10 x^3+11 x^2+23 x+11$
  • $y^2=32 x^6+10 x^5+5 x^4+22 x^3+18 x^2+4 x+37$
  • $y^2=28 x^6+19 x^5+30 x^4+9 x^3+26 x^2+24 x+17$
  • $y^2=19 x^6+17 x^5+35 x^4+37 x^3+19 x^2+12 x+13$
  • $y^2=32 x^6+20 x^5+5 x^4+17 x^3+32 x^2+31 x+37$
  • $y^2=16 x^6+x^5+18 x^4+5 x^3+22 x^2+2 x+30$
  • $y^2=5 x^6+31 x^5+37 x^4+2 x^3+7 x^2+4 x+16$
  • $y^2=30 x^6+22 x^5+17 x^4+12 x^3+x^2+24 x+14$
  • $y^2=39 x^6+20 x^5+x^4+6 x^3+7 x^2+15 x+24$
  • $y^2=x^6+20 x^5+27 x^4+17 x^3+19 x^2+4 x+30$
  • $y^2=6 x^6+38 x^5+39 x^4+20 x^3+32 x^2+24 x+16$
  • $y^2=17 x^6+2 x^5+4 x^4+40 x^3+39 x^2+x+32$
  • $y^2=20 x^6+12 x^5+24 x^4+35 x^3+29 x^2+6 x+28$
  • $y^2=12 x^6+3 x^5+20 x^4+29 x^3+22 x^2+24 x+2$
  • $y^2=31 x^6+18 x^5+38 x^4+10 x^3+9 x^2+21 x+12$
  • $y^2=5 x^6+x^5+33 x^4+16 x^3+32 x^2+38 x+3$
  • $y^2=30 x^6+6 x^5+34 x^4+14 x^3+28 x^2+23 x+18$
  • $y^2=33 x^6+28 x^5+29 x^4+10 x^3+18 x^2+6 x+26$
  • $y^2=34 x^6+4 x^5+10 x^4+19 x^3+26 x^2+36 x+33$
  • and 192 more

Decomposition and endomorphism algebra

All geometric endomorphisms are defined over $\F_{41^{2}}$.

Endomorphism algebra over $\F_{41}$
The endomorphism algebra of this simple isogeny class is \(\Q(\sqrt{5}, \sqrt{-21})\).
Endomorphism algebra over $\overline{\F}_{41}$
The base change of $A$ to $\F_{41^{2}}$ is 1.1681.c 2 and its endomorphism algebra is $\mathrm{M}_{2}($\(\Q(\sqrt{-105}) \)$)$

Base change

This is a primitive isogeny class.

Twists

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

TwistExtension degreeCommon base change
2.41.a_ac$4$(not in LMFDB)