# The arithmetic of noncongruence subgroups of $\mathrm{SL}(2,\mathbb Z)$

 Joint IAS/Princeton University Number Theory Seminar Topic: The arithmetic of noncongruence subgroups of $\mathrm{SL}(2,\mathbb Z)$ Speaker: William Chen Affiliation: Member, School of Mathematics Date: Thursday, October 27 Time/Room: 4:30pm - 5:30pm/Fine 214, Princeton University

After beginning by giving a brief overview of how one can think of noncongruence modular curves as moduli spaces of elliptic curves with G-structures, we will discuss how these moduli interpretations fits into the greater body of knowledge concerning noncongruence subgroups, in particular focusing on the Unbounded Denominators Conjecture for their modular forms.