A mixed mock modular solution of the Kaneko–Zagier equation
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The notion of mixed mock modular forms was recently introduced by Don Zagier. We show that certain solutions of the Kaneko–Zagier differential equation constitute simple yet non-trivial examples of this notion. That allows us to address a question posed by Kaneko and Koike on the (non)-modularity of these solutions.
KeywordsMixed mock modular forms Weak harmonic Maass forms Kaneko–Zagier differential equation
Mathematics Subject Classification (2010)11F12 11F37
The author is very grateful to Masanobu Kaneko for enlightening discussions and explanations related to the mathematics around equation (KZ k ). Masanobu Kaneko also read a preliminary version of this note, corrected a bunch of miscalculations and inaccuracies, and filled in some details. The author wants to take this opportunity to express his gratitude to him for doing that. The author thanks the referee for helping to improve the exposition.
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