This repository contains the code for the paper "Maps between isolated points on modular curves".

The code is divided into two directories:

• level_7 contains code for computing the isolation graph of closed points on modular curves of level 7 with j-invariant 2268945/128, see Section 6 of the paper.

• x0 contains code for computing which exceptional j-invariants can give rise to isolated points on the modular curves X_0(n), see Section 7 of the paper.

This code relies on code by Jeremy Rouse, Andrew V. Sutherland and David Zureick-Brown for computing genera of modular curves (see file groups/gl2.m in the following repository), as well as data files computed by David Zywina containing the adelic Galois image of all known exceptional j-invariants (see file data-files/exceptional_images.dat in the following repository).