Properties

Label 40.80.2-20.b.1.1
Level $40$
Index $80$
Genus $2$
Analytic rank $1$
Cusps $2$
$\Q$-cusps $2$

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Invariants

Level: $40$ $\SL_2$-level: $20$ Newform level: $400$
Index: $80$ $\PSL_2$-index:$40$
Genus: $2 = 1 + \frac{ 40 }{12} - \frac{ 0 }{4} - \frac{ 4 }{3} - \frac{ 2 }{2}$
Cusps: $2$ (all of which are rational) Cusp widths $20^{2}$ Cusp orbits $1^{2}$
Elliptic points: $0$ of order $2$ and $4$ of order $3$
Analytic rank: $1$
$\Q$-gonality: $2$
$\overline{\Q}$-gonality: $2$
Rational cusps: $2$
Rational CM points: none

Other labels

Cummins and Pauli (CP) label: 20D2
Rouse, Sutherland, and Zureick-Brown (RSZB) label: 40.80.2.2

Level structure

$\GL_2(\Z/40\Z)$-generators: $\begin{bmatrix}2&13\\21&33\end{bmatrix}$, $\begin{bmatrix}22&3\\19&14\end{bmatrix}$, $\begin{bmatrix}39&1\\5&22\end{bmatrix}$
Contains $-I$: no $\quad$ (see 20.40.2.b.1 for the level structure with $-I$)
Cyclic 40-isogeny field degree: $36$
Cyclic 40-torsion field degree: $576$
Full 40-torsion field degree: $9216$

Jacobian

Conductor: $2^{5}\cdot5^{4}$
Simple: no
Squarefree: yes
Decomposition: $1^{2}$
Newforms: 50.2.a.b, 400.2.a.a

Models

Embedded model Embedded model in $\mathbb{P}^{3}$

$ 0 $ $=$ $ x^{3} - x^{2} y + 2 x^{2} z - x^{2} w - x y^{2} + x y z + x y w - x z^{2} + y^{3} - y^{2} z $
$=$ $x^{3} - x^{2} y - x^{2} w - x y^{2} + x y z + x y w + 5 x z^{2} + y^{3} + y^{2} z + 2 y z^{2} - z w^{2}$
$=$ $3 x^{3} - 5 x^{2} y + x y^{2} + x y z - x y w + x z^{2} + x z w + y^{3} + y^{2} z + y^{2} w$
$=$ $x^{3} + x^{2} y + 2 x^{2} z - x^{2} w - x y^{2} - 5 x y z + x y w - x z^{2} - y^{3} - 3 y^{2} z + y w^{2}$
$=$$\cdots$
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Singular plane model Singular plane model

$ 0 $ $=$ $ 7 x^{4} - 2 x^{3} y - 6 x^{3} z + 2 x^{2} y^{2} - x^{2} y z - 4 x^{2} z^{2} + 2 x y^{3} + 2 x y^{2} z + \cdots + z^{4} $
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Weierstrass model Weierstrass model

$ y^{2} + \left(x^{3} + x\right) y $ $=$ $ -2x^{4} + 4x^{2} - 2 $
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Rational points

This modular curve has rational points, including 2 rational_cusps and 2 known non-cuspidal non-CM points. The following are the known rational points on this modular curve (one row per $j$-invariant).

Elliptic curve CM $j$-invariant $j$-heightPlane modelWeierstrass modelEmbedded model
no$\infty$ $0.000$
648.b1 no$-36$ $= -1 \cdot 2^{2} \cdot 3^{2}$$3.584$$(1:-2:1)$, $(0:-1:1)$$(1:-1:0)$, $(1:0:0)$$(-1/4:-1/4:-1/2:1)$, $(0:-1/2:-1/2:1)$
4418.a1 no$\tfrac{-64278657}{1024}$ $= -1 \cdot 2^{-10} \cdot 3^{3} \cdot 37^{3} \cdot 47$$17.979$$(2/3:-1/6:1)$, $(-1/3:2/3:1)$$(-1:0:1)$, $(1:-2:1)$$(-2:-3:1/2:1)$, $(-1/4:3/4:2:1)$

Maps to other modular curves

$j$-invariant map of degree 40 from the embedded model of this modular curve to the modular curve $X(1)$ :

$\displaystyle j$ $=$ $\displaystyle -\frac{92643732xyw^{7}+1830391792xz^{8}+704600656xz^{7}w+765751308xz^{6}w^{2}+1097628608xz^{5}w^{3}+932961020xz^{4}w^{4}+977869364xz^{3}w^{5}+974080990xz^{2}w^{6}-324610178xzw^{7}-46291798xw^{8}-2048y^{8}w-3072y^{7}w^{2}-2816y^{6}w^{3}+4864y^{5}w^{4}+8832y^{4}w^{5}+7056y^{3}w^{6}+459346432y^{2}z^{7}+94920256y^{2}z^{6}w+152880232y^{2}z^{5}w^{2}+221339156y^{2}z^{4}w^{3}+169133640y^{2}z^{3}w^{4}+188878224y^{2}z^{2}w^{5}+184921992y^{2}zw^{6}-92632984y^{2}w^{7}+645060848yz^{8}+262237264yz^{7}w+347178564yz^{6}w^{2}+451762414yz^{5}w^{3}+394746876yz^{4}w^{4}+418863858yz^{3}w^{5}+416515334yz^{2}w^{6}-46343278yzw^{7}+46315134yw^{8}-368z^{9}+720z^{8}w-322532064z^{7}w^{2}-131117248z^{6}w^{3}-153360434z^{5}w^{4}-204580447z^{4}w^{5}-177283027z^{3}w^{6}-186746369z^{2}w^{7}-185187568zw^{8}+46325707w^{9}}{13126xyw^{7}+636xz^{8}+2464xz^{7}w+7196xz^{6}w^{2}-9812xz^{5}w^{3}-55074xz^{4}w^{4}-23814xz^{3}w^{5}+97160xz^{2}w^{6}-30392xzw^{7}-2831xw^{8}+168y^{2}z^{7}+468y^{2}z^{6}w+1236y^{2}z^{5}w^{2}-1564y^{2}z^{4}w^{3}-9124y^{2}z^{3}w^{4}-4516y^{2}z^{2}w^{5}+15324y^{2}zw^{6}-13126y^{2}w^{7}+228yz^{8}+942yz^{7}w+2548yz^{6}w^{2}-4158yz^{5}w^{3}-19594yz^{4}w^{4}-6644yz^{3}w^{5}+33752yz^{2}w^{6}-13184yzw^{7}+2831yw^{8}-114z^{7}w^{2}-471z^{6}w^{3}-1271z^{5}w^{4}+2107z^{4}w^{5}+10019z^{3}w^{6}+3389z^{2}w^{7}-18170zw^{8}+5197w^{9}}$

Map of degree 1 from the embedded model of this modular curve to the plane model of the modular curve 20.40.2.b.1 :

$\displaystyle X$ $=$ $\displaystyle x$
$\displaystyle Y$ $=$ $\displaystyle \frac{1}{2}w$
$\displaystyle Z$ $=$ $\displaystyle y$

Equation of the image curve:

$0$ $=$ $ 7X^{4}-2X^{3}Y+2X^{2}Y^{2}+2XY^{3}-6X^{3}Z-X^{2}YZ+2XY^{2}Z-4X^{2}Z^{2}+2XYZ^{2}+2XZ^{3}+YZ^{3}+Z^{4} $

Map of degree 1 from the embedded model of this modular curve to the Weierstrass model of the modular curve 20.40.2.b.1 :

$\displaystyle X$ $=$ $\displaystyle \frac{2}{3}x-\frac{1}{6}w$
$\displaystyle Y$ $=$ $\displaystyle -\frac{26}{27}x^{3}-\frac{4}{27}x^{2}y+\frac{1}{27}x^{2}w+\frac{10}{27}xy^{2}+\frac{1}{27}xyw-\frac{2}{27}xw^{2}+\frac{4}{27}y^{3}+\frac{2}{27}y^{2}w$
$\displaystyle Z$ $=$ $\displaystyle -\frac{1}{3}x-\frac{1}{3}y-\frac{1}{6}w$

Modular covers

The following modular covers realize this modular curve as a fiber product over $X(1)$.

Factor curve Level Index Degree Genus Rank Kernel decomposition
8.16.0-4.b.1.1 $8$ $5$ $5$ $0$ $0$ full Jacobian
$X_{S_4}(5)$ $5$ $16$ $8$ $0$ $0$ full Jacobian

This modular curve minimally covers the modular curves listed below.

Covered curve Level Index Degree Genus Rank Kernel decomposition
8.16.0-4.b.1.1 $8$ $5$ $5$ $0$ $0$ full Jacobian
40.20.0-20.a.1.1 $40$ $4$ $4$ $0$ $0$ full Jacobian

This modular curve is minimally covered by the modular curves in the database listed below.

Covering curve Level Index Degree Genus Rank Kernel decomposition
40.240.8-20.f.1.4 $40$ $3$ $3$ $8$ $2$ $1^{6}$
40.240.8-20.k.1.1 $40$ $3$ $3$ $8$ $2$ $1^{6}$
40.320.9-20.g.1.2 $40$ $4$ $4$ $9$ $3$ $1^{7}$
40.320.11-40.c.1.3 $40$ $4$ $4$ $11$ $7$ $1^{7}\cdot2$
120.240.10-60.b.1.1 $120$ $3$ $3$ $10$ $?$ not computed
120.320.11-60.f.1.7 $120$ $4$ $4$ $11$ $?$ not computed