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TZID:America/Toronto
X-LIC-LOCATION:America/Toronto
BEGIN:DAYLIGHT
TZNAME:EDT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
DTSTART:20260308T070000
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TZNAME:EST
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
DTSTART:20251102T060000
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BEGIN:VEVENT
UID:6a20b3eba7779
DTSTART;TZID=America/Toronto:20260611T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260611T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-kevin
SUMMARY:Algebraic and Enumerative combinatorics seminar - Kevin Purbhoo- Th
 e\nhook length formula massacree
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Kevin Purbhoo\n\nAFFILIATION:\n University of Waterl
 oo\n\nLOCATION:\n MC 5479\n\nABSTRACT: Around 1900 Young and Frobenius (i
 ndependently\, and through\nvery different techniques) obtained a formula 
 for the dimensions of\nthe irreducible representations of the symmetric gr
 oup. Some 53 years\nlater\, Frame\, Robinson and Thrall noticed that the Y
 oung-Frobenius\nformula simplified into the now famous hook length formula
 . Nowadays\nthere are many proofs\, but the hook length formula remains so
 mething\nof a mystery\, as if some deeper understanding lies just out of r
 each.\nOne aspect of this mystery is that none of the proofs seem to indic
 ate\nhow one might come up with the formula in the first place\, other tha
 n\njust guessing.\n\nI will attempt to answer that question. It is an impr
 obable tale that\nmeanders through scenes of Young symmetrizers\, Schur-We
 yl duality\,\nWeyl algebras\, elementary combinatorics\, and Plücker rela
 tions. All\nbecause Google's AI gave me a very obviously wrong answer when
  I was\ntrying to find out the square of a Young symmetrizer.\n\nTHERE WIL
 L BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND AT\nBEGINNING GRADUATE L
 EVEL STARTING AT 1:30PM IN MC 5417.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebaaa51
DTSTART;TZID=America/Toronto:20260605T123000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260605T133000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-david-aleman-unsplittable
SUMMARY:CombOpt ReadingGroup - David Aleman-Unsplittable multicommodity flo
 ws\nin fully planar instances
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n David Aleman\n\nAFFILIATION:\n University of Water
 loo\n\nLOCATION:\n MC 6029\n\nABSTRACT: \n\nThe multicommodity flow probl
 em involves routing multiple distinct\ncommodities through a shared networ
 k. An instance is given by\nan _undirected _graph G=(V\, E(G) ) with ed
 ge capacities\, and a\ncollection of source-sink pairs (s_i\,t_i) in V wit
 h associated\nnonnegative demands d(s_i\, t_i). It will be convenient to t
 hink of the\nsource-sink pairs as forming the edges of a demand graph H=( 
 V\, E(H)\n). A flow is _feasible_ if it routes all demands without excee
 ding\nthe edge capacities\, and it is _unsplittable_ if it routes each\n
 demand along a single path. Let C be the smallest value such that the\nexi
 stence of a feasible flow implies the existence of an unsplittable\nflow t
 hat exceeds the edge capacities by at most an additivie amount\nof C times
  the maximum demand value.  \nWe show that if G+H = (V\, E(G) U E(H) ) is
  planar\, then  1.5<= C <=\n2. \nJoint work with Kumar\, Poremba\, and Sh
 epherd. 
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebab835
DTSTART;TZID=America/Toronto:20260601T140000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260601T150000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-roman-langrehr-sam-jaques-information
SUMMARY:Crypto Reading Group - Roman Langrehr & Sam Jaques-Information Set
 \nDecoding
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Roman Langrehr & Sam Jaques\n\nAFFILIATION:\n Uni
 versity of Waterloo\n\nLOCATION:\n MC 6483\n\nABSTRACT:\n\nIn this session
 \, we study information set decoding (ISD)\, one of the\nmain generic appr
 oaches for attacking code-based cryptosystems. We\nwill present the basic 
 ideas behind Prange's algorithm and Stern's\nalgorithm\, together with the
  general philosophy of decoding attacks in\nthe random-code setting. The a
 im is to understand both the algorithmic\nframework and its importance in 
 concrete security estimates.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebac655
DTSTART;TZID=America/Toronto:20260529T103000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260529T113000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-pranshu-kumar-john-premkumar-karaneh
SUMMARY:Crypto Reading Group - Pranshu Kumar & John Premkumar & Karaneh\nKe
 ypoor-Quasi-Cyclic Codes
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Pranshu Kumar & John Premkumar & Karaneh Keypoor\n
 \nAFFILIATION:\n University of Waterloo\n\nLOCATION:\n MC 5417\n\nABSTRAC
 T:\n\nThis session is devoted to quasi-cyclic codes\, one of the main\nstr
 uctured code families used in modern code-based cryptography. We\nwill int
 roduce their definition and main properties\, and explain why\ntheir addit
 ional algebraic structure is both useful for efficiency and\ndelicate from
  a security perspective. This week will provide the\nbackground needed to 
 understand HQC and related constructions.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebad255
DTSTART;TZID=America/Toronto:20260605T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260605T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-david-gosset-triply-efficient-shadow
SUMMARY:Tutte Colloquium -David Gosset-Triply efficient shadow tomography
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n David Gosset\n\nAFFILIATION:\n University of Waterlo
 o\n\nLOCATION:\n MC 5501\n\nABSTRACT:  Given copies of a quantum state\,
  a shadow tomography\nprotocol aims to learn all expectation values from a
  fixed set of\nobservables\, to within a given precision. We say that such
  a protocol\nis triply efficient if it is sample efficient\, time efficien
 t\, and\nuses measurements that entangle a constant number of copies of th
 e\nstate at a time.   A natural family of shadow tomography protocols\nb
 ased on random single-copy Clifford measurements can be understood as\nari
 sing from fractional colorings of a graph G that encodes the\ncommutation 
 structure of the set of observables. Here we describe a\nframework for two
 -copy shadow tomography that uses an initial round of\nBell measurements t
 o reduce to a fractional coloring problem in an\ninduced subgraph of G wi
 th bounded clique number. This coloring\nproblem can be addressed using te
 chniques from graph theory known as\nchi-boundedness. Using this framework
  we give the first triply\nefficient  shadow tomography scheme for the se
 t of local fermionic\nobservables\, which arise in a broad class of intera
 cting fermionic\nsystems in physics and chemistry. We also give a triply e
 fficient\nscheme for the set of all -qubit Pauli observables. Our protocol
 s for\nthese tasks use two-copy measurements\, which is necessary:\nsample
 -efficient schemes are provably impossible using only\nsingle-copy measure
 ments. This is joint work with Robbie King\, Robin\nKothari\, and Ryan Bab
 bush.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebae067
DTSTART;TZID=America/Toronto:20260604T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260604T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-theodore
SUMMARY:Algebraic and Enumerative combinatorics seminar - Theodore\nMorriso
 n-Satisfiability thresholds of linear equations over a\ncommutative ring
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Theodore Morrison\n\nAFFILIATION:\n University of Wa
 terloo\n\nLOCATION:\n MC 6460\n\nABSTRACT:The satisfiability threshold of 
 a random constraint\nsatisfaction problem (CSP) is the density of constrai
 nts at which a\nrandom CSP instance transitions from being satisfiable to\
 nunsatisfiable with high probability. Much of the research on well\nknown 
 CSPs\, including the $k$-SAT problem\, $k$-XORSAT problem\,\nhypergraph co
 louring\, and systems of linear equations\, has focused on\ndetermining sa
 tisfiability thresholds.\n\nIn this talk we consider systems of linear equ
 ations over finite\ncommutative rings as CSPs\, and build on the work of A
 yre\, Coja-Oghlan\,\nGao\, and Müller\, who determined the satisfiability
  threshold for\nrandom linear equations over a finite field. We determine 
 when the\nsatisfiability threshold is linear in the number of variables\, 
 and\nshow that any linear threshold over a principal ideal ring coincides\
 nwith the (unique) linear threshold over fields. We also determine the\nsa
 tisfiability threshold for some examples of non-principal ideal\nrings.\n\
 nThis is joint work with Jane Gao.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTI
 NG RELEVANT BACKGROUND AT\nBEGINNING GRADUATE LEVEL STARTING AT 1:30PM IN 
 MC 5417.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebaed73
DTSTART;TZID=America/Toronto:20260525T150000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260525T160000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/graphs-and-m
 atroids-stephen-arndt-approximation-algorithms
SUMMARY:Graphs and Matroids - Stephen Arndt-Approximation Algorithms for\nM
 atroid-Intersection Coloring with Applications to Rota's Basis\nConjecture
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Stephen Arndt\n\nAFFILIATION:\n Carnegie Mellon Univ
 ersity\n\nROOM:\n MC 5417\n\nABSTRACT:We study algorithmic matroid interse
 ction coloring. We give\nthe first polynomial-time O(1)-approximation algo
 rithm to color O(1)\ngeneral matroids. Notably\, for two general matroids 
 we achieve a\n2-approximation. Furthermore\, we give a fully polynomial ra
 ndomized\napproximation scheme (FPRAS) for coloring the intersection of tw
 o\nmatroids when the maximum chromatic number is large. This yields the\nf
 irst polynomial-time algorithm for an asymptotic variant of Rota's\nBasis 
 Conjecture.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebaf9fd
DTSTART;TZID=America/Toronto:20260529T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260529T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-sergio-alejandro-fernandez-soto-guerrero
SUMMARY:Tutte Colloquium -Sergio Alejandro Fernandez de Soto\nGuerrero-Posi
 triodal Magic
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Sergio Alejandro Fernandez de Soto Guerrero\n\nAFFIL
 IATION:\n TU Graz\n\nLOCATION:\n MC 5501\n\nABSTRACT: Positroids are a su
 bclass of matroids born in the study of\nthe non-negative Grassmanian by P
 ostnikov in 2006. Since then\, there\nhave been a plethora of combinatoria
 l objects indexing positroids\, two\nof these being the families of decora
 ted and bicolored permutations\,\nwhich are generalizations of classical p
 ermutations. These two\nfamilies can be used to study properties of positr
 oids\, and as a\nbyproduct we end up with useful ways to describe a group 
 action on a\ndeck of cards. In this context\, we give a definition of inva
 riants\nunder this group action allowing us\, as an application\, to devel
 op new\nmagic tricks with unusual ways of shuffling cards.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebb05bc
DTSTART;TZID=America/Toronto:20260528T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260528T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-sergio
SUMMARY:Algebraic and Enumerative combinatorics seminar - Sergio Alejandro\
 nFernandez de Soto Guerrero-New combinatorial possibilities to describe\n(
 quotients of) positroids
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Sergio Alejandro Fernandez de Soto Guerrero\n\nAFFIL
 IATION:\n TU Graz\n\nLOCATION:\n MC 5479\n\nABSTRACTPositroids were introd
 uced by Postnikov in 2006 as a special\nclass of matroids with nice combin
 atorial properties. Since 2008\,\nstarting with Suho Ho\, several attempts
  have been made to describe the\nposet of quotients for this class of matr
 oids in a combinatorial way.\nHowever\, these descriptions are incomplete 
 and always come from the\nsame perspective. That is why we will explore ne
 w combinatorial\nobjects and the context in which they arise (magic\, poly
 topes\, and\nantisymmetric algebras) to see if it is possible to describe 
 this\nposet.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND
  AT\nBEGINNING GRADUATE LEVEL STARTING AT 1:30PM IN MC 5417.
DTSTAMP:20260603T230827Z
END:VEVENT
BEGIN:VEVENT
UID:6a20b3ebb11f7
DTSTART;TZID=America/Toronto:20260515T123000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260515T133000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-kelly-dance-contract-design-beyond
SUMMARY:CombOpt ReadingGroup - Kelly Dance-Contract Design Beyond\nHidden-A
 ctions
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Kelly Dance\n\nAFFILIATION:\n University of Waterl
 oo\n\nLOCATION:\n MC 6029\n\nABSTRACT:\n\nIn the classical principal-agent
  hidden-action contract model\, a\nprincipal delegates the execution of a 
 costly task to an agent. In\norder to complete the task\, the agent choose
 s an action from a set of\nactions\, where each potential action is associ
 ated with a cost and a\nsuccess probability to accomplish the task. To inc
 entivize the agent\nto exert effort\, the principal can commit to a contra
 ct\, which is the\namount of payment based on the task's success but not o
 n the\nhidden-action chosen by the agent. \nIn this work\, we study the co
 ntract design framework under binary\noutcomes where we relax the hidden-a
 ction assumption. We introduce new\nmodels where the principal is allowed 
 to inspect subsets of actions at\nsome cost that depends on the inspected 
 subset. If the principal\ndiscovers that the agent did not select the agre
 ed-upon action through\nthe inspection\, the principal can withhold paymen
 t. This relaxation of\nthe model introduces a broader strategy space for t
 he principal\, who\nnow faces a tradeoff between positive incentives (incr
 easing payment)\nand negative incentives (increasing inspection). \nWe dev
 ise algorithms for finding the best deterministic and randomized\nincentiv
 e-compatible inspection schemes for various assumptions on the\ninspection
  cost function. In particular\, we show the tractability of\nthe case of 
 submodular inspection cost functions.  \nWE COMPLEMENT OUR RESULTS BY SHO
 WING THAT IT IS IMPOSSIBLE TO\nEFFICIENTLY FIND THE OPTIMAL RANDOMIZED INS
 PECTION SCHEME FOR THE MORE\nGENERAL CASE OF XOS INSPECTION COST FUNCTIONS
 \, AND THAT THERE IS NO\nPTAS FOR THE CASE OF SUBADDITIVE INSPECTION COST 
 FUNCTIONS.\"
DTSTAMP:20260603T230827Z
END:VEVENT
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