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SUMMARY:Juan Muñoz-Echániz (Stony Brook University)
DTSTART:20261117T150000Z
DTEND:20261117T160000Z
DTSTAMP:20261112T133742Z
UID:Geolis/186
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Geolis/186/"
 >Constraints on Lefschetz fibrations with four-dimensional fibers</a>\nby 
 Juan Muñoz-Echániz (Stony Brook University) as part of Geometria em Lisb
 oa (IST)\n\nInteractive livestream: https://tecnico-pt.zoom.us/j/995027123
 10\n\nAbstract\nI will describe constraints on the topology of Lefschetz f
 ibrations with 4-dimensional fibers (in the smooth category)\, obtained fr
 om Seiberg-Witten theory. Our main result relates the index of a Dirac ope
 rator on the total space with the monodromy of the fibration\, and is remi
 niscent of the Grothendieck-Riemann-Roch formula in the holomorphic settin
 g. As topological applications\, we construct closed simply-connected symp
 lectic 4-manifolds which admit Torelli symplectic diffeomorphisms that are
  not isotopic to products of squared Dehn twists on Lagrangian spheres\, a
 nswering a question of Donaldson in the negative. Based on joint work with
  Hokuto Konno\, Jianfeng Lin\, and Anubhav Mukherjee.\n
LOCATION:https://researchseminars.org/talk/Geolis/186/
URL:https://tecnico-pt.zoom.us/j/99502712310
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