Scri, or null-infinity, is nowadays a fundamental concept for discussing the asymptotic structure of space time. On asymptotically flat manifolds, whose asymptotic structure is modelled on the conformal compactification of Minkowski space time, scri is topologically a line bundle over a sphere. There is, however, another way to compactify Minkowski spacetime based on projective geometry. This construction leads to richer regions in the time/space like regions of the boundary at infinity than the conformal one but the null region is of codimension 2. Roughly, we've lost the fibres of the line bundle. Ashtekar's exploration of the notion of asymptotic flatness at spacelike infinity also suggests that it is also meaningful to consider a line bundle over the other regions of infinity in the projective compactification. In this talk, we consider this from a geometric perspective: what are these line bundles? Is it possible to equip them with geometric structures in a natural way? This talk is based on joint ongoing work with Yannick Herfray (Univ. Tours)

UGC Seminar webpage https://utrechtgeometrycentre.nl/ugc-seminar/

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Abstract: The quantum cohomology of the Hilb(C2,n) is determined by the operator of quantum multiplication by the divisor class (and was computed 20 years ago in work with Okounkov). I will explain how to think about the higher genus theory from several perspectives: CohFT, MNOP, and, in the case of genus 1, the intersection theory of the moduli space A_g of PPAVs. The talk is connected to recent joint and disjoint work of several mathematicians: S. Canning, F. Greer, A. Iribar Lopez, C. Lian, S. Molcho, D. Oprea, A. Pixton,and  H.-H. Tseng.

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UGC Seminar webpage https://utrechtgeometrycentre.nl/ugc-seminar/

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Title: Recent progress in the numerical bifurcation analysis of delay differential equations
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