Properties

Label 2.0.3.1-81.1-CMa1
Base field \(\Q(\sqrt{-3}) \)
Conductor norm \( 81 \)
CM yes (\(-3\))
Base change yes
Q-curve yes
Torsion order \( 9 \)
Rank \( 0 \)

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Base field \(\Q(\sqrt{-3}) \)

Generator \(a\), with minimal polynomial \( x^{2} - x + 1 \); class number \(1\).

sage: R.<x> = PolynomialRing(QQ); K.<a> = NumberField(R([1, -1, 1]))
 
gp: K = nfinit(Polrev([1, -1, 1]));
 
magma: R<x> := PolynomialRing(Rationals()); K<a> := NumberField(R![1, -1, 1]);
 

Weierstrass equation

\({y}^2+{y}={x}^{3}\)
sage: E = EllipticCurve([K([0,0]),K([0,0]),K([1,0]),K([0,0]),K([0,0])])
 
gp: E = ellinit([Polrev([0,0]),Polrev([0,0]),Polrev([1,0]),Polrev([0,0]),Polrev([0,0])], K);
 
magma: E := EllipticCurve([K![0,0],K![0,0],K![1,0],K![0,0],K![0,0]]);
 

This is a global minimal model.

sage: E.is_global_minimal_model()
 

Invariants

Conductor: \((9)\) = \((-2a+1)^{4}\)
sage: E.conductor()
 
gp: ellglobalred(E)[1]
 
magma: Conductor(E);
 
Conductor norm: \( 81 \) = \(3^{4}\)
sage: E.conductor().norm()
 
gp: idealnorm(ellglobalred(E)[1])
 
magma: Norm(Conductor(E));
 
Discriminant: \((-27)\) = \((-2a+1)^{6}\)
sage: E.discriminant()
 
gp: E.disc
 
magma: Discriminant(E);
 
Discriminant norm: \( 729 \) = \(3^{6}\)
sage: E.discriminant().norm()
 
gp: norm(E.disc)
 
magma: Norm(Discriminant(E));
 
j-invariant: \( 0 \)
sage: E.j_invariant()
 
gp: E.j
 
magma: jInvariant(E);
 
Endomorphism ring: \(\Z[(1+\sqrt{-3})/2]\) (complex multiplication)
Geometric endomorphism ring: \(\Z[(1+\sqrt{-3})/2]\)
sage: E.has_cm(), E.cm_discriminant()
 
magma: HasComplexMultiplication(E);
 
Sato-Tate group: $\mathrm{U}(1)$

Mordell-Weil group

Rank: \(0\)
Torsion structure: \(\Z/3\Z\oplus\Z/3\Z\)
sage: T = E.torsion_subgroup(); T.invariants()
 
gp: T = elltors(E); T[2]
 
magma: T,piT := TorsionSubgroup(E); Invariants(T);
 
Torsion generators: $\left(-1 : -a : 1\right)$ $\left(0 : -1 : 1\right)$
sage: T.gens()
 
gp: T[3]
 
magma: [piT(P) : P in Generators(T)];
 

BSD invariants

Analytic rank: \( 0 \)
sage: E.rank()
 
magma: Rank(E);
 
Mordell-Weil rank: \(0\)
Regulator: \( 1 \)
Period: \( 8.1086282640626946408463030203876102362 \)
Tamagawa product: \( 3 \)
Torsion order: \(9\)
Leading coefficient: \( 0.34677916377890404573710013658049705949 \)
Analytic order of Ш: \( 1 \) (rounded)

Local data at primes of bad reduction

sage: E.local_data()
 
magma: LocalInformation(E);
 
prime Norm Tamagawa number Kodaira symbol Reduction type Root number ord(\(\mathfrak{N}\)) ord(\(\mathfrak{D}\)) ord\((j)_{-}\)
\((-2a+1)\) \(3\) \(3\) \(IV\) Additive \(-1\) \(4\) \(6\) \(0\)

Galois Representations

The mod \( p \) Galois Representation has maximal image for all primes \( p < 1000 \) except those listed.

prime Image of Galois Representation
\(3\) 3Cs.1.1[2]

For all other primes \(p\), the image is a split Cartan subgroup if \(\left(\frac{ -3 }{p}\right)=+1\) or a nonsplit Cartan subgroup if \(\left(\frac{ -3 }{p}\right)=-1\).

Isogenies and isogeny class

This curve has non-trivial cyclic isogenies (excluding endomorphisms) of degree \(d\) for \(d=\) 3.
Its isogeny class 81.1-CMa consists of curves linked by isogenies of degree 3.

Base change

This elliptic curve is a \(\Q\)-curve. It is the base change of the following 2 elliptic curves:

Base field Curve
\(\Q\) 27.a4
\(\Q\) 27.a3

Additional information

This is first curve (with respect to norm of the conductor) over $\Q(\sqrt{-3})$ whose torsion subgroup is $C_3 \times C_3$.