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TZOFFSETFROM:-0500
TZOFFSETTO:-0400
DTSTART:20260308T070000
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TZOFFSETFROM:-0400
TZOFFSETTO:-0500
DTSTART:20251102T060000
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BEGIN:VEVENT
UID:6a31361be0573
DTSTART;TZID=America/Toronto:20260625T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260625T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-mike-0
SUMMARY:Algebraic and Enumerative combinatorics seminar -Mike Cummings-Webs
 \nand smooth components of two column Springer fibers
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Mike Cummings\n\nAFFILIATION:\n University of Waterl
 oo\n\nLOCATION:\n MC 6460\n\nABSTRACT:  When you encounter an algebraic 
 variety in the wild\, you\nmight ask: What do its components look like? Wh
 ich components are\nsmooth? How do the components intersect? For Springer 
 fibres\, answers\nto these questions are only known in some very special c
 ases. This is\nparticularly surprising because other aspects Springer fibr
 es have\nbeen studied for the past 50 years and they appear throughout\nco
 mbinatorics and adjacent areas. For just one example:\nHall–Littlewood p
 olynomials can be obtained from the cohomology of\nSpringer fibres by taki
 ng graded Frobenius characteristic.\n\nOne classical theorem says that the
  components of Springer fibers are\nindexed by standard Young tableaux. In
  this talk\, we will discuss the\nbenefits of instead using webs to index 
 the components in two cases:\nthe \"two row\" case\, and our recent contri
 butions in the \"two column\"\ncase. We will see that in these cases\, web
 s both characterize and\ndescribe the smooth components of Springer fibres
 \, and give a\ngeometric interpretation of rotation of webs.\n\nTHERE WILL
  BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND AT\nBEGINNING GRADUATE LE
 VEL STARTING AT 1:30PM IN MC 5417.
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be39ab
DTSTART;TZID=America/Toronto:20260619T123000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260619T133000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-kevin-cheung-home-away-pattern-set
SUMMARY:CombOpt ReadingGroup - Kevin Cheung-The home-away pattern set\nfeas
 ibility problem in sports scheduling
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Kevin Cheung\n\nAFFILIATION:\n Carleton university
 \n\nLOCATION:\n DC 2568\n\nABSTRACT:  In sports scheduling\, a single ro
 und-robin schedule for\n$2n$ teams consists of $2n-1$ rounds so that each
  team plays each of\nthe other $2n-1$ teams exactly once across the round
 s and that each\nteam plays exactly one game in each round. With each gam
 e played at\nthe venue of one of the two opposing teams\, a table of home
 -away\npatterns can be extracted from a single round-robin schedule so\nth
 at the $(i\,j)$-entry indicates whether team $i$ plays a home game\nor an
  away game in round $j$. \n\nThe home-away pattern set feasibility probl
 em turns the process around\nand asks: Given an arbitrarily constructed t
 able of home-away\npatterns\, is there a single round-robin schedule comp
 atible with it?\nEven though single round-robin schedules do not often ar
 ise in\npractice\, it is not uncommon in sports scheduling to first speci
 fy\nwhen teams should play home games and then decide on which opponents\
 nthey should play against. Being able to efficiently determine if a\nhome
 -away pattern set is feasible can help with quick generation of\npotentia
 l schedules.\n\nAs of today\, it is not known if the problem is NP-complet
 e. This talk\nwill focus on polynomial-time checkable necessary condition
 s for\nfeasibility and conditions under which they are also sufficient. S
 ome\npersonal reflections on the problem will conclude the talk.
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be4951
DTSTART;TZID=America/Toronto:20260619T103000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260619T113000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-mojtaba-fadavi-and-anna-henderson-hqc
SUMMARY:Crypto Reading Group - Mojtaba Fadavi and Anna Henderson-HQC PKE/KE
 M
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Mojtaba Fadavi and Anna Henderson\n\nAFFILIATION:\
 n University of Waterloo\n\nLOCATION:\n MC 5417\n\nABSTRACT:\n\nThis sess
 ion is devoted to the HQC cryptosystem itself\, in both its\npublic-key en
 cryption and key-encapsulation forms. We will explain how\nthe scheme work
 s\, describe its main components and design choices\, and\ndiscuss the cor
 responding security analysis\, including comments on the\npost-quantum set
 ting. By this stage\, the reading group should have\nenough background to 
 appreciate both the structure and the rationale\nof HQC. \nReferences: [1]
  and [4] \n[1] C. Aguilar-Melchor\, O. Blazy\, J.-C. Deneuville\, P. Gabor
 it and G.\nZémor. Efficient Encryption From Random Quasi-Cyclic Codes. In
  IEEE\nTransactions on Information Theory\, vol. 64\, no. 5\, pp. 3927–3
 943\,\n2018. \n[4] HQC Team. Hamming Quasi-Cyclic (HQC)\, NIST Submission\
 , 2025. \nA week-by-week plan is outlined at the following\nlink: https:/
 /www.leonardocolo.com/seminars/Spring26.html.
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be5995
DTSTART;TZID=America/Toronto:20260612T113000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260612T123000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read
 inggroup-sina-kalantarzadeh-designing-ptas
SUMMARY:CombOpt ReadingGroup - Sina Kalantarzadeh-Designing a PTAS for\nPhi
 losopher Inequalities under Constant-Depth Laminar Constraints
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Sina Kalantarzadeh\n\nAFFILIATION:\n University of
  Waterloo\n\nLOCATION:\n MC 6029\n\nABSTRACT:\n\nIn stochastic online opti
 mization\, prophet inequalities under matroid\nconstraints have been studi
 ed extensively. The philosopher\nbenchmark(optimal online strategy) is wea
 ker than the prophet\nbenchmark\, but it is still not fully understood how
  well one can\ncompete against the optimal online strategy using polynomia
 l\ncomputational power. Pashkovich and Dehaan showed that it is\nimpossibl
 e to design a PTAS for computing optimal online strategy in\ngraphic matro
 ids. \nIn this talk we consider a special class of matroid constraints so\
 ncalled laminar matroids. There are (n) items arriving in a known\norder\,
  and each item has a probability distribution over its realized\nvalue. We
  are also given a collection of bins on these items\, where\neach bin (B) 
 has a capacity (c(B)). The bins form a laminar family.\nWhen an item arriv
 es\, its value is revealed\, and the algorithm must\nimmediately decide wh
 ether to accept or reject it\, while respecting\nall laminar capacity cons
 traints. The goal is to maximize the expected\ngain of the total value of 
 the accepted items and compare it to the\ngain of the optimal online polic
 y\, rather than to the prophet.\nAnari et al. designed a polynomial-time a
 pproximation scheme(PTAS) for\nconstant-depth instances\, meaning that eac
 h item belongs to only a\nconstant number of bins. Their approach uses the
  fact that the optimal\nonline policy can be formulated as a linear progra
 m(LP). We will first\nexamine this LP in the simple case where the laminar
  family consists\nof a single bin of capacity one. In general\, however\, 
 the LP has\nexponential size and therefore cannot be solved directly in po
 lynomial\ntime. The main idea is to select certain small bins inside the l
 aminar\nfamily for which the corresponding subproblems are no longer\nexpo
 nentially large. On these selected parts\, one can use the optimal\nonline
  policy\, and then combine these local policies to obtain a\nglobal approx
 imation. It remains open whether one can design a PTAS\nfor general lamina
 r families. 
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be669f
DTSTART;TZID=America/Toronto:20260618T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260618T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-scott
SUMMARY:Algebraic and Enumerative combinatorics seminar -Scott\nNeville-Eve
 ntual sign coherence
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Scott Neville\n\nAFFILIATION:\n LACIM\n\nLOCATION:\n
  MC 6460\n\nABSTRACT: The sign coherence of c-vectors is one of the funda
 mental\ntheorems of cluster algebras with principal coefficients.  Gekhtm
 an\nand Nakanishi posed the Asymptotic Sign Coherence Conjecture for\nclus
 ter algebras with arbitrary coefficients\, which says sign\ncoherence shou
 ld eventually hold in any sufficiently generic infinite\nmutation sequence
 .  We prove that for cluster algebras from quivers\nof arbitrary rank\, t
 heir conjecture holds with probability 1 for a\nrandom mutation sequence.
   Our results also establish the conjecture\nin full generality for many 
 families of quivers.  This is joint work\nwith Amanda Burcroff.\n\nTHERE 
 WILL BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND AT\nBEGINNING GRADUAT
 E LEVEL STARTING AT 1:30PM IN MC 5417.
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be72ff
DTSTART;TZID=America/Toronto:20260612T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260612T163000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq
 uium-douglas-stebila-adding-functionality-post
SUMMARY:Tutte Colloquium -Douglas Stebila-Adding functionality to post-quan
 tum\ncryptography with variants of the Fujisaki-Okamoto transform
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Douglas Stebila\n\nAFFILIATION:\n University of Wate
 rloo\n\nLOCATION:\n MC 5501\n\nABSTRACT: The Fujisaki-Okamoto (FO) transf
 orm is a fundamental\nbuilding block in new post-quantum cryptography stan
 dards like NIST's\nML-KEM\, where it is used to convert a weakly secure pu
 blic key\nencryption scheme into a key encapsulation mechanism (KEM) secur
 e\nagainst active attackers. In this talk\, we'll explore two approaches\n
 to add extra security and functionality to post-quantum KEMs by\nenhancing
  the FO transform. First\, we see how a birthday-style\ncollision argument
  lets an attacker who collects many ciphertexts\nhalve the security of the
  FrodoKEM and HQC standards\, and how\nextending the FO transform with pub
 lic salts thwarts this multi-target\nattack. Second\, we turn to implement
 ation flaws: for 19 months\, HQC's\nreference implementation effectively s
 kipped a security-critical\nverification step\, yet basic correctness test
 s still passed. We show\nhow the principle of \"verifiable verification\"\
 , via an extension of\nthe FO transform\, ties security to functionality\,
  so that an\nimplementation which that skips it visibly breaks.
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be80b7
DTSTART;TZID=America/Toronto:20260612T103000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260612T113000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-camryn-steckel-decoding-quasi-cyclic
SUMMARY:Crypto Reading Group - Camryn Steckel-Decoding for Quasi-Cyclic Cod
 es
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Camryn Steckel\n\nAFFILIATION:\n University of Wat
 erloo\n\nLOCATION:\n MC 5417\n\nABSTRACT:\n\nThis session focuses on deco
 ding questions specific to quasi-cyclic\ncodes. We will discuss syndrome d
 ecoding in the quasi-cyclic setting\nand compare generic ISD methods with 
 approaches that exploit\nadditional structure. The goal is to better under
 stand the tension\nbetween efficiency and security\, and to prepare the gr
 ound for the\nstudy of the HQC scheme. \nReferences: [§6.3\, 4]\, [§3\, 
 6]\, and [§5\, 10] \n[4] HQC Team. Hamming Quasi-Cyclic (HQC)\, NIST Subm
 ission\, 2025. \n[6] C. Löndahl\, T. Johansson\, M. Koochak Shooshtari\, 
 M.\nAhmadian-Attari\, and M. Reza Aref. Squaring attacks on McEliece\npubl
 ic-key cryptosystems using quasi-cyclic codes of even dimension.\nDesigns\
 , Codes and Cryptography \, vol. 80\, pp. 359–377\, 2016. \n[10] N. Send
 rier. Decoding One Out of Many. Post-Quantum Cryptography.\nPQCrypto 2011.
  Lecture Notes in Computer Science\, vol. 7071\, Springer\,\n2011. \nA wee
 k-by-week plan is outlined at the following\nlink: https://www.leonardoco
 lo.com/seminars/Spring26.html.
DTSTAMP:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be8de0
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 6460\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:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361be98ed
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:20260616T114011Z
END:VEVENT
BEGIN:VEVENT
UID:6a31361bea4c6
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:20260616T114011Z
END:VEVENT
END:VCALENDAR