At the 1987 Ramanujan Centenary meeting Dyson asked for a coherent
group-theoretical structure for Ramanujan's mock theta functions analogous to
Hecke's theory of modular forms. Many of Ramanujan's mock theta functions can
be written in terms of R(ζp​,q), where R(z,q) is the two-variable
generating function of Dyson's rank function and ζp​ is a primitive
p-th root of unity. In his lost notebook Ramanujan gives the 5-dissection
of R(ζ5​,q). This result is related to Dyson's famous rank conjecture
which was proved by Atkin and Swinnerton-Dyer. In 2016 the first author showed
that there is an analogous result for the p-dissection of R(ζp​,q) when
p is any prime greater than 3, by extending work of Bringmann and Ono, and
Ahlgren and Treneer. It was also shown how the group Γ1​(p) acts on the
elements of the p-dissection of R(ζp​,q). We extend this to the group
Γ0​(p), thus revealing new and surprising symmetries for Dyson's rank
function.Comment: 51 page