I want to find the use of $q=e^{2\pi i z}$ in modular forms and combinatorics. The question here maybe a little not specific, and I'll explain it.
- I know that this is a exponential map,and map upper half plane $\mathcal{H}$ into a punctured disk. Besides, it is $\mathbb{Z}$-periodic holomorphic map. Thus, it makes modular forms which are complex functions fall into the framework of $q$-series.
However, I care about the congruent property of $q$-serises and I want to know whether there is algebraiclly convenient to change the $q$ into $e^{2\pi i z}$. To be specific, I just want more example of the use the transformation of $q=e^{2\pi i z}$ in combinatorics. Any help will be appreciated.:)