Invariants
| Level: | $9$ | $\SL_2$-level: | $9$ | ||||
| Index: | $72$ | $\PSL_2$-index: | $36$ | ||||
| Genus: | $0 = 1 + \frac{ 36 }{12} - \frac{ 0 }{4} - \frac{ 0 }{3} - \frac{ 8 }{2}$ | ||||||
| Cusps: | $8$ (none of which are rational) | Cusp widths | $1^{3}\cdot3^{2}\cdot9^{3}$ | Cusp orbits | $2\cdot3^{2}$ | ||
| Elliptic points: | $0$ of order $2$ and $0$ of order $3$ | ||||||
| $\Q$-gonality: | $1$ | ||||||
| $\overline{\Q}$-gonality: | $1$ | ||||||
| Rational cusps: | $0$ | ||||||
| Rational CM points: | yes $\quad(D =$ $-3,-27$) |
Other labels
| Cummins and Pauli (CP) label: | 9I0 |
| Rouse, Sutherland, and Zureick-Brown (RSZB) label: | 9.72.0.13 |
Level structure
| $\GL_2(\Z/9\Z)$-generators: | $\begin{bmatrix}2&7\\0&7\end{bmatrix}$, $\begin{bmatrix}5&2\\0&4\end{bmatrix}$ |
| $\GL_2(\Z/9\Z)$-subgroup: | $C_3\times D_9$ |
| Contains $-I$: | no $\quad$ (see 9.36.0.e.1 for the level structure with $-I$) |
| Cyclic 9-isogeny field degree: | $1$ |
| Cyclic 9-torsion field degree: | $6$ |
| Full 9-torsion field degree: | $54$ |
Models
This modular curve is isomorphic to $\mathbb{P}^1$.
Rational points
This modular curve has infinitely many rational points, including 8 stored non-cuspidal points.
Maps to other modular curves
$j$-invariant map of degree 36 to the modular curve $X(1)$ :
| $\displaystyle j$ | $=$ | $\displaystyle 3^6\,\frac{y^{3}x^{3}(x-y)^{3}(x+y)^{36}(x^{3}-6x^{2}y+3xy^{2}-2y^{3})^{3}(2x^{3}-3x^{2}y+6xy^{2}-4y^{3})^{3}(4x^{3}-6x^{2}y+3xy^{2}+y^{3})^{3}}{(x+y)^{36}(x^{2}-xy+y^{2})^{3}(x^{3}-6x^{2}y+3xy^{2}+y^{3})(x^{3}-3x^{2}y+y^{3})^{9}}$ |
Modular covers
This modular curve minimally covers the modular curves listed below.
| Covered curve | Level | Index | Degree | Genus | Rank |
|---|---|---|---|---|---|
| 9.24.0-9.a.1.1 | $9$ | $3$ | $3$ | $0$ | $0$ |
This modular curve is minimally covered by the modular curves in the database listed below.