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TZID:America/Toronto
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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:6a6131567e51d
DTSTART;TZID=America/Toronto:20260731T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260731T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-kanstantsin-pashkovich-simple-and-almost
SUMMARY:Tutte Colloquium -Kanstantsin Pashkovich-Simple and Almost\nNon-Ada
 ptive 1/2-Approximation for Matroid Prophet Inequalities
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Kanstantsin Pashkovich\n\nAFFILIATION:\n University 
 of Waterloo\n\nLOCATION:\n MC 5501\n\nABSTRACT: Prophet inequalities are 
 a fundamental model for online\ndecision-making under uncertainty. For mat
 roid constraints\, Kleinberg\nand Weinberg gave a tight 1/2-approximation\
 , but their algorithm uses\nadaptive thresholds that depend on the previou
 sly accepted elements.\nSpecifically\, the mechanism of Kleinberg and Wein
 berg accepts an\narriving element if and only if it is feasible to add wit
 h respect to\nthe matroid constraint and the value of the arriving element
  passes\nits threshold\; but this threshold depends on the elements accept
 ed so\nfar and on the arriving element itself. Later\, Feldman\, Svensson\
 , and\nZenklusen showed that one can give a 1/4-approximation for general\
 nmatroids. Their algorithm is almost non-adaptive\, i.e.\, it uses\nnon-ad
 aptive thresholds but changes the underlying matroid to another\n``stricte
 r'' matroid. Feldman\, Svensson\, and Zenklusen also showed\nthat no const
 ant approximation is possible in general matroids using\nnon-adaptive thre
 sholds if one does not change the underlying matroid.\n\nWe give a new alm
 ost non-adaptive algorithm for matroid prophet\ninequalities that achieves
  a 1/2 guarantee. We change the underlying\nmatroid to a ``stricter'' new 
 matroid that is a direct sum of several\nmatroids. For each part of the ne
 w matroid\, we precompute a single\nnon-adaptive threshold. Once the eleme
 nts start to arrive\, we accept\nan arriving element as long as it is feas
 ible with respect to the new\n``stricter'' matroid and its value passes th
 e precomputed threshold.\nIn addition\, we guarantee that our algorithm ac
 hieves the 1/2\nguarantee not simply with respect to the prophet's expecte
 d gain\, but\nwith respect to the stronger ex-ante relaxation value. \nThu
 s\, we provide the first almost non-adaptive algorithm for the\nmatroid pr
 ophet inequality that achieves the best-possible\napproximation guarantee 
 of 1/2. If time permits\, we will also discuss\nhow we used LLM in this pr
 oject.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a61315682f5e
DTSTART;TZID=America/Toronto:20260724T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260724T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-mahtab-alghasi-local-dyadic-conjecture
SUMMARY:CombOpt ReadingGroup -Mahtab Alghasi-The Local Dyadic Conjecture
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Mahtab Alghasi\n\nAFFILIATION:\n University of Wat
 erloo\n\nLOCATION:\n MC 6029\n\nABSTRACT: A family of sets $\\mathcal{C}$
  over a finite ground set\n$E(\\mathcal{C})$ is a clutter if no member of 
 $\\mathcal{C}$ properly\ncontains another. A clutter is ideal if its cover
 ing polyhedron is\nintegral. A rational number whose denominator is a powe
 r of two is\ncalled \\emph{dyadic}.\n\nA longstanding conjecture of Paul S
 eymour\, known as the Dyadic\nConjecture\, predicts that\, for every ideal
  clutter\, the dual of the\nset covering linear program admits an optimal 
 solution in which all\nvariables take dyadic values. We present a local ve
 rsion of this\nconjecture and provide evidence for it by proving the propo
 sed local\nstatement for binary clutters under certain assumptions. \nThis
  is joint work with Bertrand Guenin and Levent Tuncel.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a6131568466e
DTSTART;TZID=America/Toronto:20260717T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260717T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-noah-weninger-improved-algorithms
SUMMARY:CombOpt ReadingGroup - Noah Weninger-Improved algorithms for\nshort
 est-path network interdiction
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Noah Weninger\n\nAFFILIATION:\n University of Waterl
 oo\n\nLOCATION:\n MC 5029\n\nABSTRACT: \n\nIn the shortest-path network i
 nterdiction problem\, the objective is to\nselect a set $X$ of arcs in a d
 irected graph $G=(V\,A)$\, subject to a\nknapsack constraint on $X$\, such
  that the shortest $s$-$t$ path length\nin $(V\,A\\setminus X)$ is maximiz
 ed. We present an improved version of\nthe classic Israeli-Wood Benders co
 vering decomposition (2002). Our\nmethod is based on new upper and lower b
 ounds for the problem which\nintegrate cleanly into the Benders decomposit
 ion\, causing many\niterations to be skipped. Using similar techniques\, w
 e also derive new\ncovering heuristics\, which further reduce the running 
 time. In\ncomputational experiments\, our improved algorithm achieves spee
 dups of\nup to two orders of magnitude. The speedup is most notable on the
  more\ndifficult large\, dense graphs: we can often solve instances on\nco
 mplete graphs with 1000 vertices and uniformly distributed weights\nand co
 sts within a few minutes. \nThis is joint work with Amir Dadpour and Ricar
 do Fukasawa.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a61315685729
DTSTART;TZID=America/Toronto:20260724T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260724T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-francisco-j-aragon-artacho-graph-based
SUMMARY:Tutte Colloquium -Francisco J. Aragón Artacho-Graph-based splittin
 g\nalgorithms for optimization and feasibility problems
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Francisco J. Aragón Artacho\n\nAFFILIATION:\n Unive
 rsity of Alicante\n\nLOCATION:\n MC 5501\n\nABSTRACT: When an optimizatio
 n problem is structured\, it is normally\nadvantageous to use this feature
  when designing algorithms to solve\nit. Following the divide-and-conquer 
 paradigm\, splitting algorithms\niteratively solve simpler problems that a
 re defined by separately\nusing some parts of the original problem. In thi
 s talk\, we will recall\nsome classical methods and present some recent ad
 vances in this\nsubject\, paying special attention to splitting methods de
 vised by\ngraphs.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a613156867e9
DTSTART;TZID=America/Toronto:20260723T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260723T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-alexandre
SUMMARY:Algebraic and Enumerative combinatorics seminar -Alexandre Zotine-A
 \npipe dream framework for orbital varieties of type M² = 0
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Alexandre Zotine\n\nAFFILIATION:\n University of Saa
 rland\n\nLOCATION:\n MC 5479\n\nABSTRACT: An orbital scheme D of type M²
  = 0 is the closure of a\nconjugacy class of some set of n × n upper tria
 ngular matrices which\nare nilpotent of order 2. The geometric components 
 of the orbit scheme\nare called orbital varieties of type M² = 0\, and re
 cently their\ninvariants have been connected to statistical mechanics. In 
 the\nsetting of M² = 0\, there are combinatorial methods for studying the
 se\ninvariants via the action of the Borel group of upper triangular\ninve
 rtible matrices. In this talk\, we introduce a new pipe dream\nframework f
 or computing and understanding these invariants. This is\njoint work with 
 Megumi Harada\, Illya Kierkosz\, Allen Knutson\, Emma\nNaguit\, Brett Nass
 erden\, Naveena Rangunathan\, and Adam van Tuyl.\n\nTHERE WILL BE A PRE-SE
 MINAR PRESENTING RELEVANT BACKGROUND AT\nBEGINNING GRADUATE LEVEL STARTING
  AT 1:30PM IN MC 5417.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a61315687917
DTSTART;TZID=America/Toronto:20260717T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260717T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-audrey-beliveau-combinatorial-structure-and-0
SUMMARY:Tutte Colloquium -Audrey Béliveau-Combinatorial Structure and\nAlg
 orithms for Treatment Rankings
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Audrey Béliveau\n\nAFFILIATION:\n University of Wat
 erloo\n\nLOCATION:\n MC 5501\n\nABSTRACT: \n\nNetwork meta-analysis (NMA)
  enables the comparison of multiple medical\ninterventions by combining ev
 idence on their efficacy or safety across\nclinical trials. Although these
  models produce rich probabilistic\ninformation about how treatments rank\
 , what practitioners often want\nare simple\, interpretable summaries\; fo
 r example\, whether a treatment\nis likely among the best\, or whether one
  option is likely to\noutperform another. \nThe challenge is that\, with n
  treatments\, the number of possible\nquestions one can ask about permutat
 ions\, combinations\, or partial\norderings of various subsets of treatmen
 ts grows exponentially. This\nleads to a large but highly structured combi
 natorial space\, making\nexhaustive evaluation infeasible. \nWe develop al
 gorithmic methods to explore this space efficiently and\nto identify all b
 inary treatment hierarchy statements whose posterior\nprobability exceeds 
 a specified threshold (e.g.\, 95%). Our approach\nexploits structure in th
 e ranking space to avoid redundant\ncomputations and then prunes conclusio
 ns that are logically implied by\nothers\, yielding a concise and non-redu
 ndant set of results. We\nillustrate the approach on an NMA of diabetes tr
 eatments.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a61315688d05
DTSTART;TZID=America/Toronto:20260710T103000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260710T113000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-maggie-simmons-hqc-implementation-and
SUMMARY:Crypto Reading Group - Maggie Simmons-HQC Implementation and\nOptim
 ization
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Maggie Simmons\n\nAFFILIATION:\n University of Wat
 erloo\n\nLOCATION:\n MC 6029\n\nABSTRACT:\n\nThis week will cover the impl
 ementation and optimization of key\nsub-routines within HQC. We will begin
  by examining the implementation\nof Reed-Solomon decoding within HQC\, wh
 ich includes the BCH-view of\nsyndromes\, weighted Newton's identity\, the
  Berlekamp-Massey algorithm\,\nand more. We will also discuss high-perform
 ance polynomial\nmultiplication via the Karatsuba algorithm and hardware o
 ptimization. \nReferences: [3] and [4] \n[3] J. Dong\, Y. Hou\, S. Wang\, 
 L. Sha\, F. Xiao\, Z. Dong\, and J. Lin.\nHIGH: Harnessing GPU Parallelism
  for Optimized HQC Performance. In\nIACR Cryptology ePrint Archive\, 2026.
  \n[4] HQC Team. Hamming Quasi-Cyclic (HQC)\, NIST Submission\, 2025. \nA 
 week-by-week plan is outlined at the following\nlink: https://www.leonard
 ocolo.com/seminars/Spring26.html.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a61315689f32
DTSTART;TZID=America/Toronto:20260709T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260709T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-oliver
SUMMARY:Algebraic and Enumerative combinatorics seminar -Oliver\nPechenik-R
 evenge of the increasing tableau dynamics
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Oliver Pechenik\n\nAFFILIATION:\n University of Wate
 rloo\n\nLOCATION:\n MC 6460\n\nABSTRACT: Standard tableaux are certain gr
 ids of numbers that lead a\ndouble life in algebraic combinatorics\, with 
 distinct roles in\ngeometry and in representation theory. Extending the ge
 ometry to\nK-theory led to a corresponding extension of the combinatorics 
 to a\ntheory of increasing tableaux. I will discuss a longstanding plot by
 \nsuch tableaux to prevent me from explicating their combinatorial\ndynami
 cs. Despite their reticence\, we seem to be uncovering that these\ntableau
 x also have a mysterious second life in representation theory.\n\nTHERE WI
 LL BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND AT\nBEGINNING GRADUATE 
 LEVEL STARTING AT 1:30PM IN MC 5417.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a6131568affe
DTSTART;TZID=America/Toronto:20260710T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260710T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-nathan-benedetto-proenca-why-are-sdp
SUMMARY:CombOpt ReadingGroup - Nathan Benedetto Proenca-Why are SDP Roundi
 ng\nAlgorithms Randomized?
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Nathan Benedetto Proenca\n\nAFFILIATION:\n Univers
 ity of Waterloo\n\nLOCATION:\n MC 6029\n\nABSTRACT: Randomization is a po
 werful technique within theoretical\ncomputer science. There is strong th
 eoretical picture studying\ndistinct complexity models with access to ran
 dom bits\, in particular\nfocused on what types of algorithms can be de-r
 andomized. This\ndiscussion will not venture into this part of the litera
 ture\, rather\nquestioning an implicit assumption present when discussing
  the need\nfor random bits. Why is randomness helpful at all\, in partic
 ular in\nthe design of rounding algorithms in the SDP literature? Grante
 d\,\nthe value of randomness in other contexts is quite explicit. For\ne
 xample\, a quicksort implementation uses randomization to avoid worst\nca
 se inputs. The probabilistic method allows for simple constructions\nof c
 omplex objects by harvesting complexity from a randomness source.\nBut wh
 at purpose does randomness serve when rounding a SDP solution\ninto a sol
 ution to a NP-hard problem? Why Goemans and Williamson had\nto use a rand
 om hyperplane to turn vectors in the hypersphere into a\nedge-cut in a gr
 aph? This talk attempts to answer this question by\npresenting a couple 
 of theorems which connect the existence of\nrandomized rounding algorithm
 s to cornerstone results in functional\nanalysis.
DTSTAMP:20260722T210838Z
END:VEVENT
BEGIN:VEVENT
UID:6a6131568bfe5
DTSTART;TZID=America/Toronto:20260703T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260703T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-oliver-pechenik-dynamics-increasing
SUMMARY:Tutte Colloquium -Oliver Pechenik-Dynamics of Increasing Tableaux
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Oliver Pechenik\n\nAFFILIATION:\n University of Wate
 rloo\n\nLOCATION:\n MC 5501\n\nABSTRACT: Standard tableaux are certain gr
 ids of numbers that lead a\ndouble life in algebraic combinatorics\, with 
 distinct roles in\ngeometry and in representation theory. Extending the ge
 ometry to\nK-theory led to a corresponding extension of the combinatorics 
 to a\ntheory of increasing tableaux. I will discuss a long and ongoing\npr
 ogram to explicate the combinatorial dynamics of these tableaux\,\nwhich s
 eems to be revealing that they also have a mysterious second\nlife in repr
 esentation theory. Despite the algebraic connections\, the\ncore problem i
 s fundamentally combinatorial: to give a sufficiently\ngood bijection betw
 een tableaux and a set of planar diagrams. 
DTSTAMP:20260722T210838Z
END:VEVENT
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