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DTSTART:20180311T070000
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DTSTART:20171105T060000
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DTSTART;TZID=America/Toronto:20180814T100000
SEQUENCE:0
TRANSP:TRANSPARENT
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URL:https://uwaterloo.ca/pure-mathematics/events/phd-thesis-defence-7
SUMMARY:PhD Thesis Defence
CLASS:PUBLIC
DESCRIPTION:RENZHI SONG\, DEPARTMENT OF PURE MATHEMATICS\, UNIVERSITY OF WA
 TERLOO\n\n\"Series-Parallel Posets and Polymorphisms\"\n\nThe complexity o
 f the retraction problem for series-parallel posets is\nknown to be in P f
 or those that satisfy the 4-crown condition. We will\nshow how we can impr
 ove on this to show that it is in NL. Furthermore\nwe will show that satis
 fying the 4-crown condition is equivalent to\nadmitting Freese-McKenzie po
 lymorphisms. This establishes an\nequivalence between all of properties me
 ntioned above for\nseries-parallel posets. \n\nMC 2009
DTSTAMP:20260607T170348Z
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