Genus 2 curve 676.a.562432.1

• Label: 676.a.562432.1
• Conductor: $676$
• Discriminant: $562432$
• Mordell-Weil group: \(\Z/{21}\Z\)
• 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

This is a model for the modular curve $X_0(26)$.

Minimal equation

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

(, )

Invariants

Conductor:	\( N \)	\(=\)	\(676\)	\(=\)	\( 2^{2} \cdot 13^{2} \)
Discriminant:	\( \Delta \)	\(=\)	\(562432\)	\(=\)	\( 2^{8} \cdot 13^{3} \)

Igusa-Clebsch invariants

\( I_2 \)	\(=\)	\(1620\)	\(=\)	\( 2^{2} \cdot 3^{4} \cdot 5 \)
\( I_4 \)	\(=\)	\(52953\)	\(=\)	\( 3 \cdot 19 \cdot 929 \)
\( I_6 \)	\(=\)	\(29527389\)	\(=\)	\( 3^{3} \cdot 251 \cdot 4357 \)
\( I_{10} \)	\(=\)	\(71991296\)	\(=\)	\( 2^{15} \cdot 13^{3} \)

Automorphism group

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

Rational points

All points: \((1 : 0 : 0),\, (1 : -1 : 0),\, (0 : 0 : 1),\, (0 : -1 : 1)\)

Number of rational Weierstrass points: \(0\)

This curve is locally solvable everywhere.

Mordell-Weil group of the Jacobian

Group structure: \(\Z/{21}\Z\)

Generator	$D_0$						Height	Order
\(D_0 - (1 : -1 : 0) - (1 : 0 : 0)\)	\(2x^2 + xz + 3z^2\)	\(=\)	\(0,\)	\(4y\)	\(=\)	\(xz^2 - 3z^3\)	\(0\)	\(21\)

2-torsion field: 6.0.86528.1

BSD invariants

Hasse-Weil conjecture:	verified
Analytic rank:	\(0\)
Mordell-Weil rank:	\(0\)
2-Selmer rank:	\(0\)
Regulator:	\( 1 \)
Real period:	\( 6.723259 \)
Tamagawa product:	\( 21 \)
Torsion order:	\( 21 \)
Leading coefficient:	\( 0.320155 \)
Analytic order of Ш:	\( 1 \)   (rounded)
Order of Ш:	square

Local invariants

Prime	ord(\(N\))	ord(\(\Delta\))	Tamagawa	L-factor	Cluster picture
\(2\)	\(2\)	\(8\)	\(7\)	\(( 1 - T )( 1 + T )\)
\(13\)	\(2\)	\(3\)	\(3\)	\(( 1 - T )( 1 + T )\)

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?
\(2\)	2.60.2	no
\(3\)	3.2160.20	yes

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 26.a
  Elliptic curve isogeny class 26.b

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 \(\Q\).