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: | $8$ (of which $3$ are rational) | Cusp widths | $1^{3}\cdot3^{2}\cdot9^{3}$ | Cusp orbits | $1^{3}\cdot2\cdot3$ | ||
| Elliptic points: | $0$ of order $2$ and $0$ of order $3$ | ||||||
| $\Q$-gonality: | $1$ | ||||||
| $\overline{\Q}$-gonality: | $1$ | ||||||
| Rational cusps: | $3$ | ||||||
| Rational CM points: | none |
Other labels
| Cummins and Pauli (CP) label: | 9I0 |
| Rouse, Sutherland, and Zureick-Brown (RSZB) label: | 9.72.0.6 |
Level structure
| $\GL_2(\Z/9\Z)$-generators: | $\begin{bmatrix}7&1\\0&1\end{bmatrix}$, $\begin{bmatrix}7&3\\0&8\end{bmatrix}$ |
| $\GL_2(\Z/9\Z)$-subgroup: | $C_9:C_6$ |
| Contains $-I$: | no $\quad$ (see 9.36.0.d.2 for the level structure with $-I$) |
| Cyclic 9-isogeny field degree: | $1$ |
| Cyclic 9-torsion field degree: | $3$ |
| 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 20 stored non-cuspidal points.
Maps to other modular curves
$j$-invariant map of degree 36 to the modular curve $X(1)$ :
| $\displaystyle j$ | $=$ | $\displaystyle -3^3\,\frac{(x+2y)^{36}(x^{3}-3xy^{2}-y^{3})^{3}(17x^{9}+72x^{8}y+135x^{7}y^{2}+165x^{6}y^{3}+99x^{5}y^{4}-54x^{4}y^{5}-192x^{3}y^{6}-171x^{2}y^{7}-81xy^{8}-17y^{9})^{3}}{(x-y)(x+2y)^{37}(2x+y)(x^{2}+xy+y^{2})^{3}(x^{3}+3x^{2}y-y^{3})^{9}}$ |
Modular covers
This modular curve minimally covers the modular curves listed below.
| Covered curve | Level | Index | Degree | Genus | Rank |
|---|---|---|---|---|---|
| 9.24.0-9.a.1.2 | $9$ | $3$ | $3$ | $0$ | $0$ |
This modular curve is minimally covered by the modular curves in the database listed below.