Minimal Weierstrass equation
\(y^2=x^3+x^2-41x-116\) 
Mordell-Weil group structure
\(\Z/{2}\Z\)
Torsion generators
\( \left(-4, 0\right) \)
Integral points
\( \left(-4, 0\right) \)
Invariants
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sage: E.conductor().factor()
gp: ellglobalred(E)[1]
magma: Conductor(E);
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| Conductor: | \( 20 \) | = | \(2^{2} \cdot 5\) |
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sage: E.discriminant().factor()
gp: E.disc
magma: Discriminant(E);
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| Discriminant: | \(2000 \) | = | \(2^{4} \cdot 5^{3} \) |
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sage: E.j_invariant().factor()
gp: E.j
magma: jInvariant(E);
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| j-invariant: | \( \frac{488095744}{125} \) | = | \(2^{14} \cdot 5^{-3} \cdot 31^{3}\) |
| Endomorphism ring: | \(\Z\) | ||
| Geometric endomorphism ring: | \(\Z\) | (no potential complex multiplication) | |
| Sato-Tate group: | $\mathrm{SU}(2)$ | ||
| Faltings height: | \(-0.38064395118146512547640346211\dots\) | ||
| Stable Faltings height: | \(-0.61169301136811356194881416926\dots\) | ||
BSD invariants
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sage: E.rank()
magma: Rank(E);
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| Analytic rank: | \(0\) | ||
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sage: E.regulator()
magma: Regulator(E);
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| Regulator: | \(1\) | ||
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sage: E.period_lattice().omega()
gp: E.omega[1]
magma: RealPeriod(E);
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| Real period: | \(1.8829167613060758663225263660\dots\) | ||
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sage: E.tamagawa_numbers()
gp: gr=ellglobalred(E); [[gr[4][i,1],gr[5][i][4]] | i<-[1..#gr[4][,1]]]
magma: TamagawaNumbers(E);
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| Tamagawa product: | \( 1 \) | ||
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sage: E.torsion_order()
gp: elltors(E)[1]
magma: Order(TorsionSubgroup(E));
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| Torsion order: | \(2\) | ||
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sage: E.sha().an_numerical()
magma: MordellWeilShaInformation(E);
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| Analytic order of Ш: | \(1\) (exact) | ||
Modular invariants
For more coefficients, see the Downloads section to the right.
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sage: E.modular_degree()
magma: ModularDegree(E);
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| Modular degree: | 6 | ||
| \( \Gamma_0(N) \)-optimal: | no | ||
| Manin constant: | 2 | ||
Special L-value
\( L(E,1) \) ≈ \( 0.47072919032651896658063159150721550180 \)
Local data
This elliptic curve is not semistable. There are 2 primes of bad reduction:
| prime | Tamagawa number | Kodaira symbol | Reduction type | Root number | ord(\(N\)) | ord(\(\Delta\)) | ord\((j)_{-}\) |
|---|---|---|---|---|---|---|---|
| \(2\) | \(1\) | \(IV\) | Additive | -1 | 2 | 4 | 0 |
| \(5\) | \(1\) | \(I_{3}\) | Non-split multiplicative | 1 | 1 | 3 | 3 |
Galois representations
The image of the 2-adic representation attached to this elliptic curve is the subgroup of $\GL(2,\Z_2)$ with Rouse label X9c.
This subgroup is the pull-back of the subgroup of $\GL(2,\Z_2/2^3\Z_2)$ generated by $\left(\begin{array}{rr} 1 & 1 \\ 0 & 1 \end{array}\right),\left(\begin{array}{rr} 7 & 0 \\ 2 & 1 \end{array}\right),\left(\begin{array}{rr} 1 & 0 \\ 6 & 3 \end{array}\right)$ and has index 12.
The mod \( p \) Galois representation has maximal image \(\GL(2,\F_p)\) for all primes \( p \) except those listed.
| prime | Image of Galois representation |
|---|---|
| \(2\) | B |
| \(3\) | B.1.2 |
$p$-adic data
$p$-adic regulators
All \(p\)-adic regulators are identically \(1\) since the rank is \(0\).
Iwasawa invariants
| $p$ | 2 | 3 | 5 |
|---|---|---|---|
| Reduction type | add | ordinary | nonsplit |
| $\lambda$-invariant(s) | - | 2 | 0 |
| $\mu$-invariant(s) | - | 1 | 0 |
All Iwasawa $\lambda$ and $\mu$-invariants for primes $p\ge 5$ of good reduction are zero.
An entry - indicates that the invariants are not computed because the reduction is additive.
Isogenies
This curve has non-trivial cyclic isogenies of degree \(d\) for \(d=\)
2, 3 and 6.
Its isogeny class 20a
consists of 4 curves linked by isogenies of
degrees dividing 6.
Growth of torsion in number fields
The number fields $K$ of degree less than 24 such that $E(K)_{\rm tors}$ is strictly larger than $E(\Q)_{\rm tors}$ $\cong \Z/{2}\Z$ are as follows:
| $[K:\Q]$ | $K$ | $E(K)_{\rm tors}$ | Base change curve |
|---|---|---|---|
| $2$ | \(\Q(\sqrt{5}) \) | \(\Z/2\Z \times \Z/2\Z\) | 2.2.5.1-80.1-a6 |
| $2$ | \(\Q(\sqrt{-3}) \) | \(\Z/6\Z\) | 2.0.3.1-400.1-a4 |
| $3$ | 3.1.108.1 | \(\Z/6\Z\) | Not in database |
| $4$ | 4.0.320.1 | \(\Z/4\Z\) | Not in database |
| $4$ | \(\Q(\sqrt{-3}, \sqrt{5})\) | \(\Z/2\Z \times \Z/6\Z\) | Not in database |
| $6$ | 6.0.34992.1 | \(\Z/3\Z \times \Z/6\Z\) | Not in database |
| $6$ | 6.2.1458000.2 | \(\Z/2\Z \times \Z/6\Z\) | Not in database |
| $8$ | 8.4.64000000.1 | \(\Z/2\Z \times \Z/4\Z\) | Not in database |
| $8$ | 8.0.2560000.1 | \(\Z/2\Z \times \Z/4\Z\) | Not in database |
| $8$ | 8.0.8294400.2 | \(\Z/12\Z\) | Not in database |
| $12$ | 12.0.19131876000000.1 | \(\Z/6\Z \times \Z/6\Z\) | Not in database |
| $12$ | Deg 12 | \(\Z/12\Z\) | Not in database |
| $16$ | 16.0.4096000000000000.1 | \(\Z/4\Z \times \Z/4\Z\) | Not in database |
| $16$ | 16.0.1717986918400000000.1 | \(\Z/8\Z\) | Not in database |
| $16$ | 16.0.26873856000000000000.9 | \(\Z/2\Z \times \Z/12\Z\) | Not in database |
| $16$ | 16.0.42998169600000000.1 | \(\Z/2\Z \times \Z/12\Z\) | Not in database |
| $18$ | 18.0.7625597484987000000000000.3 | \(\Z/18\Z\) | Not in database |
We only show fields where the torsion growth is primitive. For fields not in the database, click on the degree shown to reveal the defining polynomial.