2 papers
math.NT2024
Quasi-Jacobi forms, Appell-Lerch functions, and false theta functions as q-brackets of functions on partitions
Kathrin Bringmann, Jan-Willem van Ittersum, Jonas Kaszian
We study certain algebras of theta-like functions on partitions, for which the corresponding generating functions give rise to theta functions, quasi-Jacobi forms, Appell-Lerch sum…
math.AG2020
Gromov-Witten theory of K3 surfaces and a Kaneko-Zagier equation for Jacobi forms
Jan-Willem van Ittersum, Georg Oberdieck, Aaron Pixton
We prove the existence of quasi-Jacobi form solutions for an analogue of the Kaneko--Zagier differential equation for Jacobi forms. The transformation properties of the solutions u…