Genus 2 curve 20172.b.968256.1

• Label: 20172.b.968256.1
• Conductor: $20172$
• Discriminant: $-968256$
• Mordell-Weil group: \(\Z \oplus \Z \oplus \Z/{2}\Z\)
• Sato-Tate group: $\mathrm{SU}(2)\times\mathrm{SU}(2)$
• \(\End(J_{\overline{\Q}}) \otimes \R\): \(\R \times \R\)
• \(\End(J_{\overline{\Q}}) \otimes \Q\): \(\Q \times \Q\)
• \(\End(J) \otimes \Q\): \(\Q \times \Q\)
• \(\overline{\Q}\)-simple: no
• \(\mathrm{GL}_2\)-type: yes

Minimal equation

$y^2 + (x^2 + x)y = x^6 - x^5 - 2x^4 + 4x^3 - 3x + 1$

(, )

Invariants

Conductor:	\( N \)	\(=\)	\(20172\)	\(=\)	\( 2^{2} \cdot 3 \cdot 41^{2} \)
Discriminant:	\( \Delta \)	\(=\)	\(-968256\)	\(=\)	\( - 2^{6} \cdot 3^{2} \cdot 41^{2} \)

Igusa-Clebsch invariants

\( I_2 \)	\(=\)	\(68\)	\(=\)	\( 2^{2} \cdot 17 \)
\( I_4 \)	\(=\)	\(193729\)	\(=\)	\( 23 \cdot 8423 \)
\( I_6 \)	\(=\)	\(-27415199\)	\(=\)	\( - 7 \cdot 613 \cdot 6389 \)
\( I_{10} \)	\(=\)	\(-123936768\)	\(=\)	\( - 2^{13} \cdot 3^{2} \cdot 41^{2} \)

Automorphism group

\(\mathrm{Aut}(X)\)	\(\simeq\)	$C_2^2$
\(\mathrm{Aut}(X_{\overline{\Q}})\)	\(\simeq\)	$C_2^2$

Rational points

Known points
\((1 : -1 : 0)\)	\((1 : 1 : 0)\)	\((-1 : 0 : 1)\)	\((0 : -1 : 1)\)	\((0 : 1 : 1)\)	\((1 : 0 : 1)\)
\((1 : -2 : 1)\)	\((1 : -3 : 2)\)	\((2 : 3 : 1)\)	\((-3 : 5 : 2)\)	\((2 : -9 : 1)\)	\((-3 : -11 : 2)\)
\((3 : -52 : 5)\)	\((3 : -68 : 5)\)

Number of rational Weierstrass points: \(2\)

This curve is locally solvable everywhere.

Mordell-Weil group of the Jacobian

Group structure: \(\Z \oplus \Z \oplus \Z/{2}\Z\)

Generator	$D_0$						Height	Order
\((-1 : 0 : 1) + (0 : 1 : 1) - (1 : -1 : 0) - (1 : 1 : 0)\)	\(x (x + z)\)	\(=\)	\(0,\)	\(y\)	\(=\)	\(xz^2 + z^3\)	\(0.158713\)	\(\infty\)
\((0 : -1 : 1) - (1 : 1 : 0)\)	\(z x\)	\(=\)	\(0,\)	\(y\)	\(=\)	\(-x^3 - z^3\)	\(0.112353\)	\(\infty\)
\((-1 : 0 : 1) + (1 : -3 : 2) - (1 : -1 : 0) - (1 : 1 : 0)\)	\((x + z) (2x - z)\)	\(=\)	\(0,\)	\(4y\)	\(=\)	\(-xz^2 - z^3\)	\(0\)	\(2\)

2-torsion field: 4.0.656.1

BSD invariants

Hasse-Weil conjecture:	verified
Analytic rank:	\(2\)
Mordell-Weil rank:	\(2\)
2-Selmer rank:	\(3\)
Regulator:	\( 0.017831 \)
Real period:	\( 16.48290 \)
Tamagawa product:	\( 8 \)
Torsion order:	\( 2 \)
Leading coefficient:	\( 0.587845 \)
Analytic order of Ш:	\( 1 \)   (rounded)
Order of Ш:	square

Local invariants

Prime	ord(\(N\))	ord(\(\Delta\))	Tamagawa	L-factor	Cluster picture
\(2\)	\(2\)	\(6\)	\(4\)	\(( 1 + T )^{2}\)
\(3\)	\(1\)	\(2\)	\(2\)	\(( 1 + T )( 1 + 2 T + 3 T^{2} )\)
\(41\)	\(2\)	\(2\)	\(1\)	\(( 1 + T )^{2}\)

Galois representations

For primes $\ell \ge 5$ the Galois representation data has not been computed for this curve since it is not generic.

For primes $\ell \le 3$, the image of the mod-$\ell$ Galois representation is listed in the table below, whenever it is not all of $\GSp(4,\F_\ell)$.

Prime \(\ell\)	mod-\(\ell\) image	Is torsion prime?
\(2\)	2.90.3	yes
\(3\)	3.90.1	no

Sato-Tate group

\(\mathrm{ST}\)	\(\simeq\)	$\mathrm{SU}(2)\times\mathrm{SU}(2)$
\(\mathrm{ST}^0\)	\(\simeq\)	\(\mathrm{SU}(2)\times\mathrm{SU}(2)\)

Decomposition of the Jacobian

Splits over \(\Q\)

Decomposes up to isogeny as the product of the non-isogenous elliptic curve isogeny classes:
  Elliptic curve isogeny class 246.a
  Elliptic curve isogeny class 82.a

Endomorphisms of the Jacobian

Of \(\GL_2\)-type over \(\Q\)

Endomorphism ring over \(\Q\):

\(\End (J_{})\)	\(\simeq\)	an order of index \(2\) in \(\Z \times \Z\)
\(\End (J_{}) \otimes \Q \)	\(\simeq\)	\(\Q\) \(\times\) \(\Q\)
\(\End (J_{}) \otimes \R\)	\(\simeq\)	\(\R \times \R\)

All \(\overline{\Q}\)-endomorphisms of the Jacobian are defined over \(\Q\).