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Properties

Label 49.a2
Conductor $49$
Discriminant $-40353607$
j-invariant \( -3375 \)
CM yes (\(D=-7\))
Rank $0$
Torsion structure \(\Z/{2}\Z\)

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Minimal Weierstrass equation

Minimal Weierstrass equation

Simplified equation

\(y^2+xy=x^3-x^2-107x+552\) Copy content Toggle raw display (homogenize, simplify)
\(y^2z+xyz=x^3-x^2z-107xz^2+552z^3\) Copy content Toggle raw display (dehomogenize, simplify)
\(y^2=x^3-1715x+33614\) Copy content Toggle raw display (homogenize, minimize)

Copy content comment:Define the curve
 
Copy content sage:E = EllipticCurve([1, -1, 0, -107, 552])
 
Copy content gp:E = ellinit([1, -1, 0, -107, 552])
 
Copy content magma:E := EllipticCurve([1, -1, 0, -107, 552]);
 
Copy content oscar:E = elliptic_curve([1, -1, 0, -107, 552])
 
Copy content comment:Simplified equation
 
Copy content sage:E.short_weierstrass_model()
 
Copy content magma:WeierstrassModel(E);
 
Copy content oscar:short_weierstrass_model(E)
 

Mordell-Weil group structure

\(\Z/{2}\Z\)

Copy content comment:Mordell-Weil group
 
Copy content magma:MordellWeilGroup(E);
 

Mordell-Weil generators

$P$$\hat{h}(P)$Order
$(-12, 6)$$0$$2$

Integral points

\( \left(-12, 6\right) \) Copy content Toggle raw display

Copy content comment:Integral points
 
Copy content sage:E.integral_points()
 
Copy content magma:IntegralPoints(E);
 

Invariants

Conductor: $N$  =  \( 49 \) = $7^{2}$
Copy content comment:Conductor
 
Copy content sage:E.conductor().factor()
 
Copy content gp:ellglobalred(E)[1]
 
Copy content magma:Conductor(E);
 
Copy content oscar:conductor(E)
 
Discriminant: $\Delta$  =  $-40353607$ = $-1 \cdot 7^{9} $
Copy content comment:Discriminant
 
Copy content sage:E.discriminant().factor()
 
Copy content gp:E.disc
 
Copy content magma:Discriminant(E);
 
Copy content oscar:discriminant(E)
 
j-invariant: $j$  =  \( -3375 \) = $-1 \cdot 3^{3} \cdot 5^{3}$
Copy content comment:j-invariant
 
Copy content sage:E.j_invariant().factor()
 
Copy content gp:E.j
 
Copy content magma:jInvariant(E);
 
Copy content oscar:j_invariant(E)
 
Endomorphism ring: $\mathrm{End}(E)$ = $\Z$
Geometric endomorphism ring: $\mathrm{End}(E_{\overline{\Q}})$  =  \(\Z[(1+\sqrt{-7})/2]\)    (potential complex multiplication)
Copy content comment:Potential complex multiplication
 
Copy content sage:E.has_cm()
 
Copy content magma:HasComplexMultiplication(E);
 
Sato-Tate group: $\mathrm{ST}(E)$ = $N(\mathrm{U}(1))$
Faltings height: $h_{\mathrm{Faltings}}$ ≈ $0.17381668547203423542836466200$
Copy content comment:Faltings height
 
Copy content gp:ellheight(E)
 
Copy content magma:FaltingsHeight(E);
 
Copy content oscar:faltings_height(E)
 
Stable Faltings height: $h_{\mathrm{stable}}$ ≈ $-1.2856159263194507434006498956$
Copy content comment:Stable Faltings height
 
Copy content magma:StableFaltingsHeight(E);
 
Copy content oscar:stable_faltings_height(E)
 
$abc$ quality: $Q$ ≈ $0.9802957926219806$
Szpiro ratio: $\sigma_{m}$ ≈ $6.693725102160739$

BSD invariants

Analytic rank: $r_{\mathrm{an}}$ = $ 0$
Copy content comment:Analytic rank
 
Copy content sage:E.analytic_rank()
 
Copy content gp:ellanalyticrank(E)
 
Copy content magma:AnalyticRank(E);
 
Mordell-Weil rank: $r$ = $ 0$
Copy content comment:Mordell-Weil rank
 
Copy content sage:E.rank()
 
Copy content gp:[lower,upper] = ellrank(E)
 
Copy content magma:Rank(E);
 
Regulator: $\mathrm{Reg}(E/\Q)$ = $1$
Copy content comment:Regulator
 
Copy content sage:E.regulator()
 
Copy content gp:G = E.gen \\ if available matdet(ellheightmatrix(E,G))
 
Copy content magma:Regulator(E);
 
Real period: $\Omega$ ≈ $1.9333117056168115467330768390$
Copy content comment:Real Period
 
Copy content sage:E.period_lattice().omega()
 
Copy content gp:if(E.disc>0,2,1)*E.omega[1]
 
Copy content magma:(Discriminant(E) gt 0 select 2 else 1) * RealPeriod(E);
 
Tamagawa product: $\prod_{p}c_p$ = $ 2 $  = $ 2 $
Copy content comment:Tamagawa numbers
 
Copy content sage:E.tamagawa_numbers()
 
Copy content gp:gr=ellglobalred(E); [[gr[4][i,1],gr[5][i][4]] | i<-[1..#gr[4][,1]]]
 
Copy content magma:TamagawaNumbers(E);
 
Copy content oscar:tamagawa_numbers(E)
 
Torsion order: $\#E(\Q)_{\mathrm{tor}}$ = $2$
Copy content comment:Torsion order
 
Copy content sage:E.torsion_order()
 
Copy content gp:elltors(E)[1]
 
Copy content magma:Order(TorsionSubgroup(E));
 
Copy content oscar:prod(torsion_structure(E)[1])
 
Special value: $ L(E,1)$ ≈ $0.96665585280840577336653841951 $
Copy content comment:Special L-value
 
Copy content sage:r = E.rank(); E.lseries().dokchitser().derivative(1,r)/r.factorial()
 
Copy content gp:[r,L1r] = ellanalyticrank(E); L1r/r!
 
Copy content magma:Lr1 where r,Lr1 := AnalyticRank(E: Precision:=12);
 
Analytic order of Ш: Ш${}_{\mathrm{an}}$  =  $1$    (exact)
Copy content comment:Order of Sha
 
Copy content sage:E.sha().an_numerical()
 
Copy content magma:MordellWeilShaInformation(E);
 

BSD formula

$$\begin{aligned} 0.966655853 \approx L(E,1) & = \frac{\# ะจ(E/\Q)\cdot \Omega_E \cdot \mathrm{Reg}(E/\Q) \cdot \prod_p c_p}{\#E(\Q)_{\rm tor}^2} \\ & \approx \frac{1 \cdot 1.933312 \cdot 1.000000 \cdot 2}{2^2} \\ & \approx 0.966655853\end{aligned}$$

Copy content comment:BSD formula
 
Copy content sage:# self-contained SageMath code snippet for the BSD formula (checks rank, computes analytic sha) E = EllipticCurve([1, -1, 0, -107, 552]); r = E.rank(); ar = E.analytic_rank(); assert r == ar; Lr1 = E.lseries().dokchitser().derivative(1,r)/r.factorial(); sha = E.sha().an_numerical(); omega = E.period_lattice().omega(); reg = E.regulator(); tam = E.tamagawa_product(); tor = E.torsion_order(); assert r == ar; print("analytic sha: " + str(RR(Lr1) * tor^2 / (omega * reg * tam)))
 
Copy content magma:/* self-contained Magma code snippet for the BSD formula (checks rank, computes analytic sha) */ E := EllipticCurve([1, -1, 0, -107, 552]); r := Rank(E); ar,Lr1 := AnalyticRank(E: Precision := 12); assert r eq ar; sha := MordellWeilShaInformation(E); omega := RealPeriod(E) * (Discriminant(E) gt 0 select 2 else 1); reg := Regulator(E); tam := &*TamagawaNumbers(E); tor := #TorsionSubgroup(E); assert r eq ar; print "analytic sha:", Lr1 * tor^2 / (omega * reg * tam);
 

Modular invariants

Modular form   49.2.a.a

\( q + q^{2} - q^{4} - 3 q^{8} - 3 q^{9} + 4 q^{11} - q^{16} - 3 q^{18} + O(q^{20}) \) Copy content Toggle raw display

Copy content comment:q-expansion of modular form
 
Copy content sage:E.q_eigenform(20)
 
Copy content gp:\\ actual modular form, use for small N [mf,F] = mffromell(E) Ser(mfcoefs(mf,20),q) \\ or just the series Ser(ellan(E,20),q)*q
 
Copy content magma:ModularForm(E);
 

For more coefficients, see the Downloads section to the right.

Modular degree: 7
Copy content comment:Modular degree
 
Copy content sage:E.modular_degree()
 
Copy content gp:ellmoddegree(E)
 
Copy content magma:ModularDegree(E);
 
$ \Gamma_0(N) $-optimal: no
Manin constant: 1
Copy content comment:Manin constant
 
Copy content magma:ManinConstant(E);
 

Local data at primes of bad reduction

This elliptic curve is not semistable. There is only one prime $p$ of bad reduction:

$p$ Tamagawa number Kodaira symbol Reduction type Root number $\mathrm{ord}_p(N)$ $\mathrm{ord}_p(\Delta)$ $\mathrm{ord}_p(\mathrm{den}(j))$
$7$ $2$ $III^{*}$ additive -1 2 9 0

Copy content comment:Local data
 
Copy content sage:E.local_data()
 
Copy content gp:ellglobalred(E)[5]
 
Copy content magma:[LocalInformation(E,p) : p in BadPrimes(E)];
 
Copy content oscar:[(p,tamagawa_number(E,p), kodaira_symbol(E,p), reduction_type(E,p)) for p in bad_primes(E)]
 

Galois representations

The $\ell$-adic Galois representation has maximal image for all primes $\ell$ except those listed in the table below.

prime $\ell$ mod-$\ell$ image $\ell$-adic image
$7$ 7B.1.2 7.48.0.3

Copy content comment:Mod p Galois image
 
Copy content sage:rho = E.galois_representation(); [rho.image_type(p) for p in rho.non_surjective()]
 
Copy content magma:[GaloisRepresentation(E,p): p in PrimesUpTo(20)];
 

The table below list all primes $\ell$ for which the Serre invariants associated to the mod-$\ell$ Galois representation are exceptional.

$\ell$ Reduction type Serre weight Serre conductor
$7$ additive $20$ \( 1 \)

Isogenies

Copy content comment:Isogenies
 
Copy content gp:ellisomat(E)
 

This curve has non-trivial cyclic isogenies of degree $d$ for $d=$ 2, 7 and 14.
Its isogeny class 49.a consists of 4 curves linked by isogenies of degrees dividing 14.

Twists

The minimal quadratic twist of this elliptic curve is 49.a4, its twist by $-7$.

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
$2$ \(\Q(\sqrt{-7}) \) \(\Z/2\Z \oplus \Z/2\Z\) 2.0.7.1-49.1-CMa1
$3$ \(\Q(\zeta_{7})^+\) \(\Z/14\Z\) 3.3.49.1-49.1-a2
$4$ 4.2.5488.1 \(\Z/4\Z\) not in database
$4$ 4.0.1372.1 \(\Z/2\Z \oplus \Z/4\Z\) not in database
$6$ \(\Q(\zeta_{7})\) \(\Z/2\Z \oplus \Z/14\Z\) not in database
$8$ 8.0.30118144.2 \(\Z/4\Z \oplus \Z/4\Z\) not in database
$8$ 8.0.30118144.1 \(\Z/2\Z \oplus \Z/8\Z\) not in database
$8$ 8.2.257298363.1 \(\Z/6\Z\) not in database
$12$ 12.6.8099130339328.1 \(\Z/28\Z\) not in database
$12$ 12.0.126548911552.1 \(\Z/2\Z \oplus \Z/28\Z\) not in database
$16$ 16.4.59447875862838378496.1 \(\Z/8\Z\) not in database
$16$ 16.0.232218265089212416.1 \(\Z/4\Z \oplus \Z/8\Z\) not in database
$16$ deg 16 \(\Z/2\Z \oplus \Z/16\Z\) not in database
$16$ 16.0.66202447602479769.1 \(\Z/6\Z \oplus \Z/6\Z\) not in database
$20$ 20.0.11194501700250570391613.1 \(\Z/2\Z \oplus \Z/22\Z\) 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.

Iwasawa invariants

$p$ 2 3 5 7
Reduction type ord ss ss add
$\lambda$-invariant(s) ? 0,0 0,0 -
$\mu$-invariant(s) ? 0,0 0,0 -

All Iwasawa $\lambda$ and $\mu$-invariants for primes $p\ge 11$ of good reduction are zero.

An entry ? indicates that the invariants have not yet been computed.

An entry - indicates that the invariants are not computed because the reduction is additive.

$p$-adic regulators

All $p$-adic regulators are identically $1$ since the rank is $0$.

Additional information

This curve $E$ is the quotient of the Fermat curve $F_7$ of degree $7$ by the action of $S_3$ that permutes the variables of the symmetrical form $X^7 + Y^7 + Z^7 = 0$ of $F_7$. Since $E$ has rank zero (and that fact can be shown by descent using the rational $2$-isogeny), this yields a proof of the exponent-$7$ case of Fermat's last theorem that is almost as elementary as Fermat's for $n=4$ (and certainly easier than the known proofs for $n=5$). This proof was given by Genocchi in 1855: he wrote, towards the end of his paper "Intorno all'equazione $x^7+y^7+z^7 = 0$", Annali di Mat. Pura ed Applicata 6 (1864), 287-288), that he announced these results in "Cimento di Torino, vol. VI, fasc. VIII, 1855"; see pages 75-76 of [https://library.slmath.org/books/Book35/files/elkies.pdf]. By a result of Gross and Rohrlich published in Inventiones Math. 1978 [https://link.springer.com/article/10.1007/BF01403161], the Jacobian of $F_p$ has infinite order for all primes $p>7$, suggesting that Genocchi's elementary proof for $p=7$ is the last one of its kind.