Tu's elliptic expansion conjecture for the modular j-function

Let s(w)=2πΩ2S(w)s(w)=2\pi\Omega^2S(w) be the rescaled inverse mirror-map coordinate, and let g(t)g(t) and h(t)h(t) be the power series associated with the elliptic quartic as defined above. Around the hexagonal point and the square point, use the corresponding local expansions of the modular jj-function. Elliptic expansion conjecture. Around the hexagonal point,

j(s1(h(t)g(t)))=27t3(8t31+t3)3=13824t346656t6+99144t9171315t12+263169t15,j\left(s^{-1}\left(\frac{h(t)}{g(t)}\right)\right)=27t^3\left(\frac{8-t^3}{1+t^3}\right)^3 =13824t^3-46656t^6+99144t^9-171315t^{12}+263169t^{15}-\cdots,

and around the square point,

j(s1(h(t)g(t)))=(192+256t)(3+4t14t2)2=1728+20736t2+147456t4+851968t6+4456448t8+.j\left(s^{-1}\left(\frac{h(t)}{g(t)}\right)\right)=(192+256t)\left(\frac{3+4t}{1-4t^2}\right)^2 =1728+20736t^2+147456t^4+851968t^6+4456448t^8+\cdots.

These identities would relate the categorical Saito-theoretic flat coordinates for the elliptic quartic to the classical modular parameter, extending the analogous description for Fermat cubics; the source provides no resolution, so the conjecture remains open.

Sources & referencesView supporting material

Primary source

Andrei Caldararu, Yunfan He and Shengyuan Huang, “Moonshine at Landau-Ginzburg points”, arXiv:2107.12405 (2021).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.