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SUMMARY:Li Yuezhao
DTSTART:20200708T081500Z
DTEND:20200708T094500Z
DTSTAMP:20260530T010610Z
UID:GoettingenNCG/6
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/GoettingenNC
 G/6/">Coarse Mayer-Vietoris Sequence and Bulk-Edge Correspondence</a>\nby 
 Li Yuezhao as part of Göttingen Seminar Noncommutative Geometry\n\n\nAbst
 ract\nRoe C*-algebras are models of topological insulators.  The bulk inva
 riants are given by their K-theory.  The bulk-edge correspondence claims t
 hat non-trivial bulk invariants lead to the existence of edge states.  In 
 a recent preprint\, Ludewig and Thiang constructed an integer-valued map t
 o compute the bulk invariants and proved that the spectral gap closes if t
 he map is non-zero.  They used a partition of the space\, but showed also 
 that the map does not depend much on the partition.\n\nIn this talk\, I wi
 ll show that the map defined by Ludewig and Thiang agrees with a compositi
 on of boundary maps in coarse Mayer-Vietoris sequences.  The insensitivity
  to partitions is a consequence of the naturality of the coarse Mayer-Viet
 oris sequence.  The boundary maps in coarse Mayer-Vietoris sequences descr
 ibe the bulk-edge correspondence.  These results can be generalised to hig
 her-dimensional spaces.\n
LOCATION:https://researchseminars.org/talk/GoettingenNCG/6/
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