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TZOFFSETFROM:-0500
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DTSTART:20240310T070000
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TZOFFSETFROM:-0400
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DTSTART:20241103T060000
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BEGIN:VEVENT
UID:672bd9000ba2c
DTSTART;TZID=America/Toronto:20241107T140000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241107T150000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
d-enumerative-combinatorics-seminar-stephan
SUMMARY:Algebraic and enumerative combinatorics seminar-Stephan\nPfannerer-
Mittas
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE:Descents for Border Strip Tableaux\n\nSpeaker
\n Stephan Pfannerer-Mittas\n\nAffiliation\n University of Waterloo\n\nLoc
ation\n MC 5479\n\n ABSTRACT: Lusztig's fake degree is the generating pol
ynomial for the\nmajor index of standard Young tableaux of a given shape.
Results of\nSpringer and James & Kerber imply that\, mysteriously\, its ev
aluation\nat a d-th primitive root of unity yields the number of border st
rip\ntableaux with all strips of size d\, up to sign. This is essentially\
nthe special case of the Murnaghan-Nakayama rule for rectangular\npartitio
ns as cycle type. We refine this result to standard Young\ntableaux and bo
rder strip tableaux with a given number of descents. To\ndo so\, we introd
uce a new descent statistic for border strip tableaux\,\nextending the cla
ssical definition for standard Young tableaux.\n\nTHERE WILL BE A PRE-SEMI
NAR PRESENTING RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTI
NG AT 1PM\,\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9000d4fa
DTSTART;TZID=America/Toronto:20241108T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241108T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
uium-r-tyrell-rockafellar
SUMMARY:Tutte colloquium-R. Tyrell Rockafellar
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Problem Decomposition in Optimization: Alg
orithmic Advances\nBeyond ADMM\n\nSPEAKER:\n R. Tyrell Rockafellar\n\nAFFI
LIATION:\n The University of Washington\n\nLOCATION:\n Main Hall\, Federat
ion Hall \n\nABSTRACT: \n\nDecomposition schemes like those coming from AD
MM typically start by\nposing a separable-type problem in the Fenchel dual
ity format. They\nthen pass to an augmented Lagrangian\, which however c
an interfere with\nthe separability and cause a slow-down. Progressive d
ecoupling\noffers a more flexible approach which can utilize augmented\nLa
grangians while maintaining decomposability. Based on a variable\nmetric
extension of the proximal point algorithm that's applied in a\ntwisted so
rt of way\, progressive decoupling benefits from stopping\ncriteria which
can guarantee convergence despite inexact minimization\nin each iteration.
The convergence is generically at a linear\nrate\, and for convex pro
blems\, is global. But the method also works\nfor nonconvex problems when
initiated close enough to a point that\nsatisfies a natural extension of t
he strong sufficient condition for\nlocal optimality known from nonlinear
programming. \n\nThis talk is held as part of the 26th Annual Midwest Opti
mization\nMeeting (“MOM26”).\n\n \n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9000ddb9
DTSTART;TZID=America/Toronto:20241114T140000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241114T150000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
d-enumerative-combinatorics-seminar-colleen
SUMMARY:Algebraic and enumerative combinatorics seminar-Colleen Robichaux
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE:Complexity of structure constants\n\nSpeaker\
n Colleen Robichaux\n\nAffiliation\n UCLA\n\nLocation\n MC 5479\n\n ABSTR
ACT: In algebraic combinatorics many families of polynomials\nhave non-neg
ative integral structure constants. Several open problems\nseek to provide
manifestly positive combinatorial formulas for these\ncoefficients. In pa
rt one of this talk\, we prove the existence of\nsigned combinatorial form
ulas for many families of structure\nconstants. In the second part\, we
narrow our discussion towards\nSchubert structure constants. We discuss th
eir complexity and explore\npotential implications. This is joint work wit
h Igor Pak.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND
AT THE\nBEGINNING GRADUATE LEVEL STARTING AT 1PM\,\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9000e4dd
DTSTART;TZID=America/Toronto:20241104T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241104T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-gr
aph-theory-he-guo
SUMMARY:Algebraic Graph Theory-He Guo
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Intersection of Matroids\n\nSPEAKER:\n He Gu
o\n\nAFFILIATION:\n Umeå University\n\nLOCATION:\n Please contact Sabrin
a Lato for Zoom link.\n\nABSTRACT: We study simplicial complexes (hypergr
aphs closed under\ntaking subsets) that are the intersection of a given nu
mber k of\nmatroids. We prove bounds on their chromatic numbers (the minim
um\nnumber of edges required to cover the ground set) and their list\nchro
matic numbers. Settling a conjecture of Kiraly and\nBerczi--Schwarcz--Yama
guchi\, we prove that the list chromatic number\nis at most k times the ch
romatic number. The tools used are in part\ntopological. If time permits\,
I will also discuss a result proving\nthat the list chromatic number of t
he intersection of two matroids is\nat most the sum of the chromatic numb
ers of each matroid\, improving a\nresult by Aharoni and Berger from 2006.
The talk is based on works\njoint with Ron Aharoni\, Eli Berger\, and Dan
iel Kotlar. In this talk\,\nthere is no assumption about background knowle
dge of matroid theory or\nalgebraic topology.\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9000eca4
DTSTART;TZID=America/Toronto:20241031T140000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241031T150000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
d-enumerative-combinatorics-seminar-joseph
SUMMARY:Algebraic and enumerative combinatorics seminar-Joseph Fluegemann
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE:Smooth points on positroid varieties and plan
ar N=4\nsupersymmetric Yang-Mills theory\n\nSpeaker\n Joseph Fluegemann\n\
nAffiliation\n University of Waterloo\n\nLocation\n MC 5479\n\n ABSTRACT:
Positroid varieties are subvarieties in the Grassmannian\ndefined by cycl
ic rank conditions and which are related to Schubert\nvarieties. We will p
rovide a criterion for whether positroid varieties\nare smooth at certain
distinguished points\, and we will show that this\ninformation is sufficie
nt to determine smoothness for the entire\npositroid variety. This will in
volve looking at combinatorial diagrams\ncalled \"affine pipe dreams.\" We
can also form a partial order on\npositroid varieties given by deletion a
nd contraction\, such that there\nis closure for smooth positroid varietie
s\, and we will characterize\nthe minimal singular elements in this order.
Finally\, we will discuss\na couple of connections between the techniques
of this work and planar\nN=4\n\nSYM: the BCFW bridge decomposition and in
verse soft factors.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTING RELEVANT BAC
KGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTING AT 1PM\,\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9000f391
DTSTART;TZID=America/Toronto:20241028T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241028T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-gr
aph-theory-roberto-hernandez-palomares
SUMMARY:Algebraic Graph Theory-Roberto Hernández Palomares
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Quantum graphs\, subfactors and tensor categ
ories\n\nSPEAKER:\n Roberto Hernández Palomares\n\nAFFILIATION:\n Univers
ity of Waterloo\n\nLOCATION:\n Please contact Sabrina Lato for Zoom link
.\n\nABSTRACT: Graphs and their noncommutative analogues are interesting\n
objects of study from the perspectives of operator algebras\, quantum\ninf
ormation and category theory. In this talk we will introduce\n equivarian
t graphs with respect to a quantum symmetry along with\nexamples such as c
lassical graphs\, Cayley graphs of finite groupoids\,\nand their quantum a
nalogues. We will also see these graphs can be\nconstructed concretely by
modeling a quantum vertex set by an\ninclusion of operator algebras and th
e quantum edge set by an\nequivariant endomorphism that is an idempotent w
ith respect to\nconvolution/Schur product. Equipped with this viewpoint an
d tools from\nsubfactor theory\, we will see how to obtain all these idemp
otents\nusing higher relative commutants and the quantum Fourier transform
.\nFinally\, we will state a quantum version of Frucht's Theorem\, showing
\nthat every quasitriangular finite quantum groupoid arises as certain\nau
tomorphisms of some categorified graph.\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9000fa2a
DTSTART;TZID=America/Toronto:20241025T123000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241025T133000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/co-reading-g
roup-parth-mittal
SUMMARY:C&O Reading Group - Parth Mittal
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE:Nearly optimal communication and query comple
xity of bipartite\nmatching \n\nSPEAKER:\n Parth Mittal\n\nAFFILIATION:\n
University of Waterloo\n\nLOCATION:\n MC 6029\n\nABSTRACT:I will talk abo
ut a recent paper (Blikstad\, van den Brand\,\nEfron\, Mukhopadhyay\, Nano
ngkai\, FOCS 22) which gives near-optimal\nalgorithms for bipartite matchi
ng (and several generalizations) in\ncommunication complexity\, and severa
l types of query complexity. We\nwill focus only on the simplest case (i.e
. unweighted bipartite\nmatching)\,and will not assume any background on c
ommunication or query\ncomplexity.\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd900100c5
DTSTART;TZID=America/Toronto:20241024T140000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241024T150000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
d-enumerative-combinatorics-seminar-nick-olson
SUMMARY:Algebraic and enumerative combinatorics seminar-Nick Olson-Harris
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE:Sufficient conditions for equality of skew Sc
hur functions\n\nSpeaker\n Nick Olson-Harris\n\nAffiliation\n University o
f Waterloo\n\nLocation\n MC 5479\n\n ABSTRACT: : A pair of skew shapes ar
e said to be skew equivalent if\nthey admit the same number of semistandar
d Young tableaux of each\nweight\, or in other words if the skew Schur fun
ctions they define are\nequal. A conjecture of McNamara and van Willigenbu
rg gives necessary\nand sufficient combinatorial conditions for shapes to
be skew\nequivalent\, but neither direction was known to hold in general.
We\nprove sufficiency. The techniques used are Hopf-algebraic in spirit\na
nd extend ideas used by Yeats to prove a simple case.\n\nTHERE WILL BE A P
RE-SEMINAR PRESENTING RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEVEL
STARTING AT 1PM\,\n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd9001071c
DTSTART;TZID=America/Toronto:20241021T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241021T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-gr
aph-theory-ralihe-raul-villagran
SUMMARY:Algebraic Graph Theory-Ralihe Raul Villagran
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Determinantal ideals of graphs\n\nSPEAKER:\n
Ralihe Raul Villagran\n\nAFFILIATION:\n Worcester Polytechnic Institute\n
\nLOCATION:\n Please contact Sabrina Lato for Zoom link.\n\nABSTRACT: Le
t $A$ ($D$) denote the adjacency (distance) matrix of a\ngraph $G$ with $n
$ vertices. We define the $k$-th determinantal ideal\nof $M_X:=diag(x_1\,x
_2\,\\ldots \,x_n)+M$ as the ideal generated by all of\nits minors of size
$k\\leq n$. If $M=A$\, we call this the $k$-th\ncritical ideals of $G$. O
n the other hand\, if $M=D$\, we call it the\n$k$-th distance ideals of $G
$. These algebraic objects are related to\nthe spectrum of their correspon
ding graph matrices\, their Smith normal\nform\, and in consequence to the
ir sandpile group for instance. In this\ntalk\, we will explore some of th
e properties and applications of these\nideals. \n
DTSTAMP:20241106T210048Z
END:VEVENT
BEGIN:VEVENT
UID:672bd90010de1
DTSTART;TZID=America/Toronto:20241025T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20241025T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
uium-subhadip-singha
SUMMARY:Tutte colloquium-Subhadip Singha
CLASS:PUBLIC
DESCRIPTION:Summary \n\nTITLE: Concrete analysis of a few aspects of lattic
e-based\ncryptography\n\nSPEAKER:\n Subhadip Singha\n\nAFFILIATION:\n Univ
ersity of Waterloo\n\nLOCATION:\n MC 5501\n\nABSTRACT: A seminal 2013 pape
r by Lyubashevsky\, Peikert\, and Regev\nproposed using ideal lattices as
a foundation for post-quantum\ncryptography\, supported by a polynomial-ti
me security reduction from\nthe approximate Shortest Independent Vectors P
roblem (SIVP) to the\nDecision Learning With Errors (DLWE) problem in idea
l lattices. In our\nconcrete analysis of this multi-step reduction\, we fi
nd that the\nreduction’s tightness gap is so significant that it undermi
nes any\nmeaningful security guarantees. Additionally\, we have concerns a
bout\nthe feasibility of the quantum aspect of the reduction in the near\n
future. Moreover\, when making the reduction concrete\, the\napproximation
factor for the SIVP problem turns out to be much larger\nthan anticipated
\, suggesting that the approximate SIVP problem may not\nbe hard for the p
roposed cryptosystem parameters.\n\n \n
DTSTAMP:20241106T210048Z
END:VEVENT
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