buondì,
vi annuncio il seminario di geometria di domani mattina alle 11. Siete tutti invitati, a presto, Bruno Martelli
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12-May-2016 - 11:00 Sala Seminari (Dip. Matematica) http://www.dm.unipi.it/webnew/it/aula/sala-seminari-dip-matematica Dijkgraaf-Witten invariants over Z_2 for orientable 3-manifolds http://www.dm.unipi.it/webnew/it/seminari/dijkgraaf-witten-invariants-over-z2-orientable-3-manifolds Sergei Matveev
We will describe a general method for calculating DW-invariants of orientable 3-manifolds. The method is based on a relation between DW-invariants and Arf-invariants of special quadratic functions over Z_2 on the first cohomology group of the given manifold. As an example, we calculate DW-invariants of all orientable Seifert manifolds fibered over the 2-dimensional sphere.