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SUMMARY:Martin Tancer (Charles University Prague)
DTSTART:20210218T150000Z
DTEND:20210218T170000Z
DTSTAMP:20260422T065458Z
UID:CJCS/5
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/CJCS/5/">The
  unbearable hardness of unknotting</a>\nby Martin Tancer (Charles Universi
 ty Prague) as part of Copenhagen-Jerusalem Combinatorics Seminar\n\n\nAbst
 ract\nDuring the talk\, I will sketch a proof that deciding if a diagram o
 f the unknot can be untangled using at most k Riedemeister moves (where k 
 is part of the input) is NP-hard. (This is not the same as the unknot reco
 gnition but it reveals some difficulties.) Similar ideas can be also used 
 for proving that several other similar invariants are NP-hard to recognize
  on links.\n\nJoint work with A. de Mesmay\, Y. Rieck and E. Sedgwick.\n
LOCATION:https://researchseminars.org/talk/CJCS/5/
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