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SUMMARY:Anne Moreau (U. Paris Saclay)
DTSTART:20210107T100000Z
DTEND:20210107T113000Z
DTSTAMP:20260404T111103Z
UID:Darboux/1
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/Darbo
 ux/1/">Nilpotent Slodowy slices and W-algebras</a>\nby Anne Moreau (U. Par
 is Saclay) as part of Darboux Seminar\n\nLecture held in Amphi Charpak\, C
 ampus Pierre et Marie Curie\, Tour 22 RdJ.\n\nAbstract\nTo any vertex alge
 bra one can attach in a canonical way a certain Poisson variety\, called t
 he associated variety. Nilpotent Slodowy slices appear as associated varie
 ties of admissible (simple) W-algebras. They also appear as Higgs branches
  of the Argyres-Douglas theories in 4d N=2 SCFT’s. These two facts are l
 inked by the so-called Higgs branch conjecture. In this talk I will explai
 n how to exploit the geometry of nilpotent Slodowy slices to study some pr
 operties of W-algebras whose motivation stems from physics. This is a join
 t work with Tomoyuki Arakawa and Jethro van Ekeren (still in preparation).
 \n
LOCATION:https://stable.researchseminars.org/talk/Darboux/1/
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SUMMARY:Johannes Kellendonk (Institut Camille Jordan\, Lyon)
DTSTART:20210204T100000Z
DTEND:20210204T113000Z
DTSTAMP:20260404T111103Z
UID:Darboux/2
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/Darbo
 ux/2/">The non-commutative topological approach to topological phases with
  protecting symmetry</a>\nby Johannes Kellendonk (Institut Camille Jordan\
 , Lyon) as part of Darboux Seminar\n\nLecture held in Zoom.\n\nAbstract\nI
 n this talk we review the K-theoretic description of topological phases of
  insulators and superconductors in the effective one particle approximatio
 n. In that approximation\, an insulator (or superconductor) is described b
 y a Hamiltonian whose spectrum has a gap at the Fermi energy. Two Hamilton
 ians belong to the same topological phase if they can be deformed into eac
 h other without closing the gap. For this to be well-defined\, it is impor
 tant to specify the space of possible Hamiltonians with its topology. When
  this space is taken to be a C*-algebra equipped with a real structure and
  a grading\, one can use real graded K-theory and its dual (K-homology or 
 cyclic cohomology) to describe the topological phases and their numerical 
 topological invariants.\n
LOCATION:https://stable.researchseminars.org/talk/Darboux/2/
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