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DTSTART:20230312T070000
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DTSTART:20231105T060000
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DTSTART;TZID=America/Toronto:20231108T143000
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URL:https://uwaterloo.ca/pure-mathematics/events/logic-seminar-50
SUMMARY:Logic Seminar
CLASS:PUBLIC
DESCRIPTION:JING ZHANG\, UNIVERSITY OF TORONTO\n\n\"COMPACTNESS AND INCOMP
 ACTNESS IN HIGHER DIMENSIONAL COMBINATORICS\"\n\nWe describe an organizin
 g framework to study higher dimensional\ninfinitary combinatorics based on
  \\v{C}ech cohomology\, originating\nfrom works by Barry Mitchell\, Barbar
 a Osofsky and others. A central\ncombinatorial notion is $n$-dimensional c
 oherence sequences\,\ngeneralizing the 1-dimensional ones studied extensiv
 ely by Todorcevic\nusing the method of minimal walks. We will discuss ZFC 
 results\nsuggesting $\\aleph_n$ is not \"compact for $(n+1)$-dimensional\n
 combinatorics\" and consistency results that any regular cardinal\ngreater
  or equal to $\\aleph_{\\omega+1}$ can be \"compact for\n$n$-dimensional c
 ombinatorics for all $n$\". The talk will be purely\ncombinatorial. Joint 
 work with Jeffrey Bergfalk and Chris\nLambie-Hanson.\n\nMC 5479
DTSTAMP:20260505T204710Z
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