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TZOFFSETFROM:-0500
TZOFFSETTO:-0400
DTSTART:20240310T070000
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TZOFFSETFROM:-0400
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DTSTART:20231105T060000
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BEGIN:VEVENT
UID:6698546c4b926
DTSTART;TZID=America/Toronto:20240726T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240726T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
uium-carla-groenland
SUMMARY:Tutte Colloquium - Carla Groenland
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Tight bounds for reconstructing graphs from
distance queries\n\nSPEAKER:\n Carla Groenland\n\nAFFILIATION:\n TU Delft
\n\nLOCATION:\n MC 5501\n\nABSTRACT: Suppose you are given the vertex set
of a graph and you\nwant to discover the edge set. An oracle can tell you
\, given two\nvertices\, what the distance is between these vertices in th
e graph.\n(For example\, in a computer network\, this would represent the
minimum\nnumber of communication links needed to send a message from one\n
computer to another.) Based on the answer\, you may select the next\nquery
. The (labelled) graph is reconstructed when there is a single\nedge set c
ompatible with the answers. How many queries are needed\, in\nthe worst ca
se? The question becomes interesting for bounded degree\ngraphs. We provid
e tight bounds for various classes of graphs\,\nimproving both the lower a
nd upper bound\, in both the randomized and\ndeterministic setting. \n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c4ee1c
DTSTART;TZID=America/Toronto:20240718T140000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240718T150000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-en
umerative-combinatorics-laura-pierson
SUMMARY:Algebraic & Enumerative Combinatorics - Laura Pierson
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Two variations of the chromatic symmetric f
unction\n\nSPEAKER:\n Laura Pierson\n\nAFFILIATION:\n University of Waterl
oo\n\nLOCATION:\n MC 5479\n\nABSTRACT: The /chromatic symmetric function/
is a symmetric function\ngeneralization of the chromatic polynomial that
encodes the ways to\ncolor a graph such that no two adjacent vertices get
the same color.\nWe will discuss two different analogues of the chromatic
symmetric\nfunction: a K-theoretic analogue called the /Kromatic symmetr
ic\nfunction/\, and a categorification called the /chromatic symmetric\nho
mology/. We show that certain properties of a graph can be recovered\ngive
n its Kromatic symmetric function\, and we give some formulas for\nspecial
cases of the chromatic symmetric homology.\n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c4f7fb
DTSTART;TZID=America/Toronto:20240712T130000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240712T140000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/co-reading-g
roup-sina-kalantarzadeh
SUMMARY:C&O Reading Group - Sina Kalantarzadeh
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Approximating Graphic TSP with matchings\n\
nSPEAKER:\n Sina Kalantarzadeh\n\nAFFILIATION:\n University of Waterloo\n\
nLOCATION:\n MC 6029\n\nABSTRACT: Revisiting defining character of the fi
eld of algorithm\ndesign and complexity\, TSP!. While the problem itself i
s NP-Hard and\ndifficult to approximate\, various formulations\, such as t
he Metric\nversion\, have yielded notable approximation algorithms. The cl
assical\n1.5-approximation algorithm by Christofides\, leveraging matching
s\,\nstood as the best-known result for decades. However\, recent\nbreakth
roughs have pushed these boundaries further.\n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c50173
DTSTART;TZID=America/Toronto:20240719T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240719T161500
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
uium-paul-seymour
SUMMARY:Tutte Colloquium - Paul Seymour
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Nearly-linear stable sets\n\nSPEAKER:\n Pau
l Seymour\n\nAFFILIATION:\n Princeton University\n\nLOCATION:\n QNC 0101\n
\nABSTRACT: The Gyárfás-Sumner conjecture says that for every forest\n
𝐻 and complete graph 𝐾\, there exists 𝑐 such that every\n{𝐻\,
𝐾}-free graph (that is\, containing neither of 𝐻\,𝐾 as an\ninduce
d subgraph) has chromatic number at most 𝑐. This is still\nopen\, but w
e have proved that every {𝐻\,𝐾}-free graph 𝐺 has\nchromatic numbe
r at most |𝐺|o(1).\n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c509a5
DTSTART;TZID=America/Toronto:20240709T133000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240709T143000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/ura-seminar-
kanstantsin-pashkovich
SUMMARY:URA Seminar - Kanstantsin Pashkovich
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Contracts for Functions Based on Graphs\n\n
SPEAKER:\n Kanstantsin Pashkovich\n\nAFFILIATION:\n University of Waterloo
\n\nLOCATION:\n MC 5479\n\nABSTRACT: We study contracts for combinatorial
problems in\nmulti-agent settings. In this problem\, a principal designs
a contract\nwith several agents\, whose actions the principal is unable to
observe.\nThe principal is able to see only the outcome of the agents'\nc
ollective actions\; and the outcome is either a success or failure.\nAll
agents that decided to exert effort incur costs\, and so naturally\nall ag
ents expect a fraction of the principal's reward as a\ncompensation. The p
rincipal needs to decide what fraction of their\nreward to give to each ag
ent so that the principal's expected utility\nis maximized. \n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c51423
DTSTART;TZID=America/Toronto:20240712T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240712T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
uium-patricia-klein
SUMMARY:Tutte Colloquium - Patricia Klein
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Combinatorial models in enumerative geometr
y\n\nSPEAKER:\n Patricia Klein\n\nAFFILIATION:\n Texas A&M University\n\nL
OCATION:\n MC 5501\n\nABSTRACT: How many circles are tangent to three giv
en circles in the\nplane? How many lines lie on a smooth cubic surface?
How many lines\nintersect four given lines in 3-space? These are classical
questions\nin enumerative geometry\, a field at least as old as Apolloniu
s of\nPerga\, to whom the question about tangent circles is attributed in
the\nthird century BCE. It is not hard to see that the answers to these\
nquestions may depend on the choice of circles\, surface\, or lines\,\nre
spectively. It is harder to see that\, in each case\, there is a\n\"typica
l\" answer. \n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c51e6f
DTSTART;TZID=America/Toronto:20240702T133000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240702T143000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/ura-seminar-
thomas-lesgourgues
SUMMARY:URA Seminar - Thomas Lesgourgues
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: On the use of senders in Ramsey Theory\n\nS
PEAKER:\n Thomas Lesgourgus\n\nAFFILIATION:\n University of Waterloo\n\nLO
CATION:\n MC 5479\n\nABSTRACT: In this talk I will introduce and investig
ate some\nparameters in Graph Ramsey theory\, beyond the traditional Ramse
y\nnumbers. A crucial ingredient for their analysis is the existence of\ng
adget graphs\, called signal senders\, that were initially developed by\nB
urr\, Erdős and Lovász in 1976. I will explain their origin\,\npropertie
s\, and try to convey their surprising strength. Using\nprobabilistic meth
ods\, we will see how to build such gadgets\, and how\nto use them to prov
e some theorems\, previously out of reach without\nthese tools. \n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c52a50
DTSTART;TZID=America/Toronto:20240705T130000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240705T140000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/co-reading-g
roup-rian-neogi-4
SUMMARY:C&O Reading Group - Rian Neogi
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Bipartite Perfect Matching is in Quasi-NC\,
Part II\n\nSPEAKER:\n Rian Neogi\n\nAFFILIATION:\n University of Waterloo
\n\nLOCATION:\n MC 6029\n\nABSTRACT: Mulmuley\, Vazirani\, and Vazirani g
ave a randomized parallel\nalgorithm for checking whether a perfect matchi
ng exists in a graph.\nIn doing so\, they came up with the infamous isolat
ion lemma\, which\nfound several uses in other areas of computer science.
The isolation\nlemma is inherently randomized\, and it has been a long-sta
nding open\nproblem to derandomize the lemma. In this talk\, I will go ove
r the\nbreakthrough work of Fenner\, Gurjar\, and Thierauf where they almo
st\ncompletely derandomize the isolation lemma in the special case when\na
pplied to the bipartite perfect matching problem. In doing so\, they\ngive
a deterministic parallel algorithm for perfect matching that uses\na quas
i-polynomial number of processors.\n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c534d7
DTSTART;TZID=America/Toronto:20240705T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240705T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
uium-leonardo-colo
SUMMARY:Tutte Colloquium - Leonardo Colo
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Supersingular isogeny graphs\, modular curv
es and Galois\nRepresentations.\n\nSPEAKER:\n Leonardo Colo'\n\nAFFILIATIO
N:\n University of Waterloo\n\nLOCATION:\n MC 5501\n\nABSTRACT: In this t
alk we will discuss the remarkable interconnection\namong supersingular el
liptic curves\, modular curves and Galois\nrepresentations with a focus on
cryptographic applications.\n
DTSTAMP:20240717T233156Z
END:VEVENT
BEGIN:VEVENT
UID:6698546c53e15
DTSTART;TZID=America/Toronto:20240702T150000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20240702T160000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/graphs-and-m
atroids-bertrand-guenin
SUMMARY:Graphs and Matroids - Bertrand Guenin
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: A relaxation of Woodall’s conjecture\n\nS
PEAKER:\n Bertrand Guenin\n\nAFFILIATION:\n University of Waterloo\n\nLOCA
TION:\n MC 5479\n\nABSTRACT: In a directed graph\, a directed cut (dicut
for short) is a\ncut where all arcs are directed from one shore to the oth
er\; a\ndirected join (dijoin for short) is a set of arcs whose contractio
n\nmakes the digraph strongly connected. The celebrated\nLucchesi–Younge
r theorem states that for any directed graph the size\nof the smallest dij
oin equals the maximum number of pairwise disjoint\ndicuts. Woodall’s co
njecture posits that the size of the smallest\ndicut equals the maximum nu
mber of pairwise disjoint dijoins. \n
DTSTAMP:20240717T233156Z
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