Beyond Mock Modularity: Elliptic Corrections for Higher Dyson Ranks
Claudia Alfes, Ken Ono, Ashvin Swaminathan
math.NT
Jul 14, 2026 · v1
math.CO
TL;DR
Key new q-series formulas for higher Dyson rank corrections were formalized and machine-verified in Lean/Mathlib by AxiomProver.
Abstract
When $m = 1$, the Dyson rank generating function is a classical bridge between partition theory, Ramanujan's mock theta functions, and the theory of harmonic Maass forms and nonholomorphic Jacobi forms. The rank is a statistic on partitions, and the higher Dyson systems, for $m \geq 2$, are a natural multivariable refinement of it, combining $m$ graded rank contributions. Unlike the classical case, these higher systems are not expected to fit the mock-modular framework, which raises the question of what analytic structure governs them. We show that their root-of-unity specializations carry a hidden elliptic structure. A finite $q$-difference recurrence produces an explicit polynomial obstruction to the expected index $m$ elliptic transformation law, and because the obstruction is finite, its partial fractions canonically determine finitely many Appell–Lerch correction terms that remove it. The corrected functions satisfy a twisted index $m$ elliptic law; a natural translation removes the twist, and their holomorphic finite parts admit finite theta decompositions. Thus, the natural analogue of Dyson's mock-modular phenomenon at higher $m$ is not mock modularity but a finite theta decomposition governed by an index $m$ elliptic transformation law. These results grew out of a human–AI collaboration, and the key new formulas were formalized and machine-verified in Lean/Mathlib by AxiomProver.
Problem
Higher Dyson rank generating functions (m >= 2) are not expected to fit the mock-modular framework that governs the classical rank (m = 1), leaving open what analytic structure controls them.
Approach
Root-of-unity specializations of the higher Dyson systems are studied via a finite q-difference recurrence extracted from the deformed sequence X_j^(m)(x;q). The recurrence produces an explicit polynomial obstruction to the expected index-m elliptic transformation law, whose partial fractions determine finitely many Appell-Lerch correction terms. The corrected functions satisfy a twisted index-m elliptic law that a translation removes. Key new formulas were formalized and machine-verified in Lean/Mathlib by AxiomProver.
Results
The corrected functions satisfy an index-m elliptic transformation law, and their holomorphic finite parts admit finite theta decompositions, replacing mock modularity. The smallest new case m = 2, d = 5 is worked out explicitly with a cubic defect polynomial and corrections on five fifth-torsion orbits.