Buondì,

Vi annuncio che oggi (alle 16) e giovedì prossimo (sempre alle 16) ci saranno due seminari sulle 4-varietà. Seguono più informazioni. A presto, Bruno

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05-Oct-2017 - 16:00 Sala Seminari (Dip. Matematica) Rohlin’s theorem and non-simply connected 4-manifolds Danny Ruberman (Brandeis University)

Most applications of gauge theory in 4-dimensional topology are concerned with simply-connected manifolds with non-trivial second homology. I will discuss the opposite situation, first describing the classical Rohlin invariant for manifolds with first homology = Z and vanishing second homology. I will give an interpretation in terms of a Seiberg-Witten theory, with an unusual index-theoretic correction term. I will discuss recent work with Jianfeng Lin and Nikolai Saveliev giving a new formula for this invariant in terms of monopole homology.

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12-Oct-2017 - 16:00 Sala Seminari (Dip. Matematica) On corks with low shadow-complexity Hironobu Naoe (Tohoku University, Japan)

A cork is a contractible Stein domain that gives arise to exotic pairs of 4-manifolds. The first example was found by Akbulut. It is known that any two exotic, simply-connected, closed 4-manifolds are related by a cork twist. We show that there are no corks having shadow-complexity zero. We also show that there are infinitely many corks having shadow-conplexity 1 and 2.