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SUMMARY:Operator systems and extensions of positive semi-definite function
 s [Oberseminar Global Analysis and Operator Algebras]
DTSTART:20260602T121500Z
DTEND:20260602T134500Z
DTSTAMP:20260607T031100Z
UID:indico-event-1367@math-events.uni-bonn.de
DESCRIPTION:Speakers: Malte Leimbach (MPIM Bonn)\n\nThe extension problem 
 is a classical problem from harmonicanalysis\, and asks whether positive s
 emi-definite functions on asymmetric unital subset of a discrete group can
  be extended to positivesemi-definite functions on the whole group. It has
  been known at leastsince the work of Rudin in the 1960s that this is clos
 ely related to theproblem of finding sums of squares factorisations of pos
 itive elementsin the group C*-algebra. In this talk I will give an operato
 r systemperspective at these two problems\, explaining their equivalence\,
  and howthey are linked to the question about duality of the operator syst
 emswhich have recently emerged from spectral and Fourier truncations innon
 commutative geometry. I will also provide some background on therequired o
 perator system techniques\, and give discuss some examples fromour point o
 f view. Based on arXiv:2603.29958\, joint with EvgeniosKakariadis\, Ivan T
 odorov\, and Walter van Suijlekom.\n\nhttps://math-events.uni-bonn.de/even
 t/1367/
LOCATION:Endenicher Allee 60/1-008 (Mathezentrum)
URL:https://math-events.uni-bonn.de/event/1367/
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