BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Drupal iCal API//EN X-WR-CALNAME:Events items teaser X-WR-TIMEZONE:America/Toronto BEGIN:VTIMEZONE TZID:America/Toronto X-LIC-LOCATION:America/Toronto BEGIN:DAYLIGHT TZNAME:EDT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 DTSTART:20260308T070000 END:DAYLIGHT BEGIN:STANDARD TZNAME:EST TZOFFSETFROM:-0400 TZOFFSETTO:-0500 DTSTART:20251102T060000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:6a07b115989c1 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:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b1159c350 DTSTART;TZID=America/Toronto:20260522T103000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260522T113000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi ng-group-maher-mamah-elle-wen-introduction-code SUMMARY:Crypto Reading Group - Maher Mamah & Elle Wen-Introduction to\nCode -Based Cryptography (Part 2) CLASS:PUBLIC DESCRIPTION:SPEAKER:\n\n Maher Mamah & Elle Wen\n\nAFFILIATION:\n Universit y of Waterloo\n\nLOCATION:\n MC 5417\n\nABSTRACT:\n\nThis week\, we conti nue our discussion of codes by introducing the\nunderlying hard problem: t he decoding problem\, which asks us to decode\na random linear code. We al so discuss McEliece\, one of the oldest\ncode-based public-key encryption schemes\, and its instantiations using\nGoppa codes. DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b1159d50c DTSTART;TZID=America/Toronto:20260522T153000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260522T163000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq uium-sophie-spirkl-cliques-and-colouring SUMMARY:Tutte Colloquium -Sophie Spirkl-Cliques and colouring in tournament s CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Sophie Spirkl\n\nAFFILIATION:\n University of Waterl oo\n\nLOCATION:\n MC 5501\n\nABSTRACT: A tournament is an orientation of a complete graph\, and in\nterms of structural questions\, tournaments are often a natural\nanalogue of graphs. Neumann-Lara\, in 1982\, defined wha t it means to\ncolour a tournament. Only recently\, in 2023\, Aboulker\, A ubian\, Charbit\nand Lopes defined what the clique number of a tournament is — but it\nis a bit more complicated than in graphs. What can we say a bout these\nparameters\, from a structural and computational point of view ? There\nare a few things to say\, including a recent joint result with Lo gan\nCrew\, Xinyue Fan\, Hidde Koerts\, and Ben Moore. \n\n[MANY OF YOU KN OW THE SEVERE CONSEQUENCES THAT A COVID INFECTION HAS\nHAD FOR MY FAMILY. I WOULD CONSIDER IT A KINDNESS IF ATTENDEES WOULD\nWEAR MASKS. I WILL PROV IDE FREE MASKS FOR THOSE WHO MAY NEED THEM.] DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b1159e1cf DTSTART;TZID=America/Toronto:20260521T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260521T153000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an d-enumerative-combinatorics-seminar-kaveh SUMMARY:Algebraic and Enumerative combinatorics seminar - Kaveh Mousavand-L eft\nmodularity and extremality of some (finite and infinite) lattices via \nrepresentation theory CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Kaveh Mousavand\n\nAFFILIATION:\n Okinawa Institute of Science and Technology\n\nLOCATION:\n MC 5479\n\nABSTRACT:Motivated by the representation theory of finite-dimensional\nalgebras\, we recently in vestigated the notions of left modularity and\nextremality in (completely) semidistributive lattices. For lattices of\ntorsion classes\, we obtain a simultaneous characterization of left\nmodularity and extremality in term s of the behavior of certain\nindecomposable modules\, called bricks. Our results extend the\nclassical theory beyond the realm of finite lattices\, while remaining\nwithin the framework of (completely) semidistributive la ttices. Time\npermitting\, I will also discuss extensions of these results to\narbitrary infinite lattices that are completely semidistributive and\ nweakly atomic. This talk is based on recent joint work with Sota Asai\,\n Osamu Iyama\, and Charles Paquette.\n\nTHERE WILL BE A PRE-SEMINAR PRESENT ING RELEVANT BACKGROUND AT\nBEGINNING GRADUATE LEVEL STARTING AT 1:30PM IN MC 5417. DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b1159edac DTSTART;TZID=America/Toronto:20260515T103000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260515T113000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi ng-group-seunghoon-lee-bruno-sterner SUMMARY:Crypto Reading Group - Seunghoon Lee & Bruno Sterner-Introduction t o\nCoding Theory (Part 1) CLASS:PUBLIC DESCRIPTION:SPEAKER:\n\n Seunghoon Lee & Bruno Sterner\n\nAFFILIATION:\n Un iversity of Waterloo\n\nLOCATION:\n MC 5417\n\nABSTRACT:\n\nFor this term 's reading group\, we will be hosting a study group on\ncode-based cryptog raphy with a focus on understanding HQC — the most\nrecent NIST standard for post-quantum KEM/PKE. We will spend 7 weeks\ngoing over the necessary material to cover this topic before\nconcluding with state-of-the-art HQC . A week-by-week plan is outlined\nat the following\nlink: https://www.le onardocolo.com/seminars/Spring26.html. \nFor the first week\, we will cove r the basic definitions and properties\nof coding theory as well as go ove r Reed-Solomon codes. DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b1159fbef DTSTART;TZID=America/Toronto:20260515T153000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260515T163000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq uium-jim-geelen-tangles-graphs-and-matroids SUMMARY:Tutte Colloquium -Jim Geelen-Tangles in graphs and matroids CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Jim Geelen\n\nAFFILIATION:\n University of Waterloo\ n\nLOCATION:\n MC 5501\n\nABSTRACT: A common strategy in many proofs and algorithms is to begin\nby decomposing a graph into more highly connected pieces.\nDecomposition is easy when the goal is to obtain connected or\n2- connected pieces\, and decomposition into 3- or 4-connected pieces is\nals o straightforward in many settings. For higher levels of\nconnectivity\, h owever\, no effective and widely applicable notion of\ndecomposition is cu rrently known. To address this\, Robertson and\nSeymour introduced _tangl es_\, which capture the k-connected regions\nof a graph without decomposin g.  DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b115a09f1 DTSTART;TZID=America/Toronto:20260505T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260505T153000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an d-enumerative-combinatorics-seminar-siddhartha SUMMARY:Algebraic and Enumerative combinatorics seminar - Siddhartha\nSahi- Hypergeometric functions of matrix argument CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Siddhartha Sahi\n\nAFFILIATION:\n Rutgers University \n\nLOCATION:\n MC 6029\n\nABSTRACT:In a widely circulated manuscript from the 1990s\, I.G.\nMacdonald introduced certain higher-rank analogs of the classical\nhypergeometric functions $_pF_q$\, which are expressed as expl icit\nseries in Jack and Macdonald polynomials in one and two sets of\nvar iables. For special choices of parameters\, these series reduce to\nthe hy pergeometric functions of matrix argument introduced earlier by\nC. Herz a nd A.T. James\, which have numerous applications in number\ntheory\, multi variate statistics\, signal processing\, and random matrix\ntheory.\n\nThe classical hypergeometric functions are solutions to the\nhypergeometric d ifferential equation. Macdonald raised the problem of\nproviding an analog ous characterization for higher-rank functions by\nmeans of differential e quations. Over the years\, this problem was\nsolved for a small number of cases where p and q are at most 3.\nHowever\, as the operators become incr easingly complicated\, the general\nproblem remained open for 40 years. In this talk\, we will present a\ncomplete solution. This is joint work with Hong Chen.\n\nTHERE WILL BE A PRE-SEMINAR AT 1:30PM IN MC 6029 IN A FLIPP ED\nCLASSROOM FORMAT BASED ON MACDONALD’S MANUSCRIPT ON HYPERGEOMETRIC\n FUNCTIONS (HTTPS://ARXIV.ORG/ABS/1309.4568\n[https://arxiv.org/abs/1309.45 68]). PARTICIPANTS ARE EXPECTED TO READ\nTHE MANUSCRIPT IN ADVANCE\, AND T HE SESSION WILL FOCUS ON QUESTIONS AND\nDISCUSSION LED BY THE SPEAKER. DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b115a17b6 DTSTART;TZID=America/Toronto:20260423T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260423T153000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an d-enumerative-combinatorics-seminar-melissa SUMMARY:Algebraic and Enumerative combinatorics seminar - Melissa Ulrika\nS herman-Bennett-Dimer face polynomials in knot theory and cluster\nalgebras CLASS:PUBLIC DESCRIPTION:SPEAKER:\n\nMelissa Ulrika Sherman-Bennett \n\nAFFILIATION:\n U niversity of California\, Davis\n\nLOCATION:\n MC 5417\n\nABSTRACT: The s et of dimers (aka perfect matchings) of a connected\nbipartite plane graph G is a distributive lattice\, as shown by Propp.\nThe order relation on t his lattice comes from the \"height\" of a dimer\,\nwhich is a vector of n onnegative integers. In this talk\, I'll focus on\nthe dimer face polynomi al of G\, which is the height generating\nfunction of all dimers of G. Thi s polynomial has close connections to\nknot invariants on the one hand\, a nd cluster algebras on the other.\nI'll discuss joint work with Mészáros \, Musiker and Vidinas in which\nwe explore these connections. No knowledg e of knot theory or cluster\nalgebras will be assumed.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTING RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEV EL STARTING AT 1:30PM. DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b115a24de DTSTART;TZID=America/Toronto:20260416T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260416T153000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an d-enumerative-combinatorics-seminar-tyler SUMMARY:Algebraic and Enumerative combinatorics seminar - Tyler\nDunaisky-C osmological Correlators and Triangulating the Dual\nCosmological Polytope CLASS:PUBLIC DESCRIPTION:SPEAKER:\n\nTyler Dunaisky \n\nAFFILIATION:\n Purdue University \n\nLOCATION:\n MC 5417\n\nABSTRACT: A cosmological correlator is an Eule r integral\, associated\nto a graph G\, which encodes information about th e state of the early\nuniverse. Evaluation of these integrals is extremely challenging\, even\nin simple cases. However\, it turns out the integrand can be identified\nwith the so-called canonical form of the cosmological polytope\,\nrevealing a rich combinatorial structure and allowing the appl ication\nof techniques from commutative algebra. I'll sketch my contributi on to\nthis story and advertise the fledgling field of positive geometry\, \nwhich seeks to generalize the notion of canonical forms to geometric\nob jects more exotic than polytopes.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTIN G RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTING AT 1:30PM . DTSTAMP:20260515T234941Z END:VEVENT BEGIN:VEVENT UID:6a07b115a35bd DTSTART;TZID=America/Toronto:20260410T153000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260410T163000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq uium-tammy-kolda-fast-and-accurate-tensor SUMMARY:Tutte Colloquium -Tammy Kolda -Fast and Accurate Tensor Decompositi ons\non Infinite-Dimensional Function Spaces CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Tammy Kolda\n\nAFFILIATION:\n MathSci.ai\n\nLOCATION :\n MC 5501\n\nABSTRACT: Tensor decompositions are fundamental tools in s cientific\ncomputing and data analysis. In many applications — such as\n simulation data on irregular grids\, surrogate modeling for\nparameterized PDEs\, or spectroscopic measurements — the data has\nboth discrete and continuous structure\, and may only be observed at\nscattered sample point s. The CP-HIFI (hybrid infinite-finite)\ndecomposition generalizes the Can onical Polyadic (CP) tensor\ndecomposition to settings where some factors are finite-dimensional\nvectors and others are functions drawn from infini te-dimensional\nspaces — a natural framework when the underlying data ha s continuous\nstructure. The decomposition can be applied to a fully obser ved tensor\n(aligned) or\, when only scattered observations are available\ , to a\nsparsely sampled tensor (unaligned). Current methods compute CP-HI FI\nfactors by solving a sequence of dense linear systems arising from\nre gularized least-squares problems\, but these direct solves become\ncomputa tionally prohibitive as problem size grows. We propose new\nalgorithms tha t achieve the same accuracy while being orders of\nmagnitude faster. For a ligned tensors\, we exploit the Kronecker\nstructure of the system to effi ciently compute its eigendecomposition\nwithout ever forming the full syst em\, reducing the solve to\nindependent scalar equations. For unaligned te nsors\, we introduce a\npreconditioned conjugate gradient method applied t o a reformulated\nsystem with favorable spectral properties. We analyze th e\ncomputational complexity and memory requirements of the new methods\nan d demonstrate their effectiveness on problems with smooth functional\nmode s. I will also discuss the “First Proof” project\, which aims\nto unde rstand the capabilities of AI systems on problems that come up\nin math re search\, and the role that results from that experiment\nplayed in this pr oject. DTSTAMP:20260515T234941Z END:VEVENT END:VCALENDAR