University COVID-19 update

The University of Waterloo is constantly updating our most Frequently Asked Questions.

Questions about buildings and services? Visit the list of Modified Services.

Please note: The University of Waterloo is closed for all events until further notice.

PhD Thesis DefenceExport this event to calendar

Tuesday, August 14, 2018 — 10:00 AM EDT

Renzhi Song, Department of Pure Mathematics, University of Waterloo

"Series-Parallel Posets and Polymorphisms"

The complexity of the retraction problem for series-parallel posets is known to be in P for those that satisfy the 4-crown condition. We will show how we can improve on this to show that it is in NL. Furthermore we will show that satisfying the 4-crown condition is equivalent to admitting Freese-McKenzie polymorphisms. This establishes an equivalence between all of properties mentioned above for series-parallel posets. 

MC 2009

S M T W T F S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
1
2
3
4
5
  1. 2020 (91)
    1. November (10)
    2. October (4)
    3. September (3)
    4. August (1)
    5. July (5)
    6. June (1)
    7. May (3)
    8. March (16)
    9. February (26)
    10. January (22)
  2. 2019 (199)
    1. December (7)
    2. November (26)
    3. October (19)
    4. September (13)
    5. August (7)
    6. July (12)
    7. June (18)
    8. May (22)
    9. April (11)
    10. March (25)
    11. February (17)
    12. January (22)
  3. 2018 (212)
  4. 2017 (281)
  5. 2016 (335)
  6. 2015 (211)
  7. 2014 (235)
  8. 2013 (251)
  9. 2012 (135)