Logarithmic vector-valued modular forms

Marvin Knopp; Geoffrey Mason

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arXiv · 0910.3976

Logarithmic vector-valued modular forms

Marvin Knopp·Geoffrey Mason

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Abstract

We consider logarithmic vector- and matrix-valued modular forms of integral weight $k$ associated with a $p$-dimensional representation $ρ: SL_2(\mathbb{Z}) \to GL_p(\mathbb{C})$ of the modular group, subject only to the condition that $ρ(T)$ has eigenvalues of absolute value 1. The main result is the construction of meromorphic matrix-valued Poincaré series associated to $ρ$ for all large enough weights. The component functions are logarithmic $q$-series, i.e., finite sums of products of $q$-series and powers of $\log q$. We derive several consequences, in particular we show that the space $\mathcal{H}(ρ)=\oplus_k \mathcal{H}(k, ρ)$ of all holomorphic logarithmic vector-valued modular forms associated to $ρ$ is a free module of rank $p$ over the ring of classical holomorphic modular forms on $SL_2(\mathbb{Z})$.

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Marvin Knopp, Geoffrey Mason. 2009-10-20. Logarithmic vector-valued modular forms. https://arxiv.org/abs/0910.3976

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