= Monodromy eigenfunction Laurent representation
{c}
For a linear <ordinary differential equation> with <holomorphic> coefficients on a punctured disc, analytic continuation of a basis gives an invertible <monodromy> matrix. A nonzero <eigenvector> with <eigenvalue> $\lambda=e^{2\pi i\sigma}$ selects a solution $w$ for which $z^{-\sigma}w$ is single-valued and <holomorphic>. Its <Laurent series> gives $w=z^\sigma\sum_{n\in\mathbb Z}c_nz^n$. No regular-singular hypothesis is needed; infinitely many negative powers may occur.
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