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Autori: A. Dimca, S. Papadima, A.I. Suciu
Editorial: Mathematische Zeitschrift, 268 (1), p.169-186, 2011.
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.
Cuvinte cheie: Quasi-Kähler manifold, 3-manifold, Cut number, Isolated surface singularity, 1-formal group, Cohomology ring, Characteristic variety, Resonance variety