Abstract
In this note, we address the following question: Which 1-formal groups occur as fundamental groups of both quasi-Kähler manifolds and closed, connected,
orientable 3-manifolds. We classify all such groups, at the level of Malcev completions,
and compute their coranks. Dropping the assumption on realizability by 3-manifolds,
we show that the corank equals the isotropy index of the cup-product map in degree one.
Finally, we examine the formality properties of smooth affine surfaces and quasi-homogeneous
isolated surface singularities. In the latter case, we describe explicitly the
positive-dimensional components of the first characteristic variety for the
associated singularity link.
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