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:6ad668fc522ac DTSTART;TZID=America/Toronto:20261019T150000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261019T160000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/graphs-and-m atroids-emanuel-juliano-morais-silva-connection SUMMARY:Graphs and Matroids | Emanuel Juliano Morais Silva\, On the connect ion\nbetween max-cuts\, the vector chromatic number\, and random sphere\ng raphs CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Emanuel Juliano Morais Silva\n\nAFFILIATION:\n Unive rsity of Waterloo\n\nROOM:\n MC 6029\n\nABSTRACT: It is well known that t he maximum cut size of a graph is at\nleast half its number of edges. But how small can this difference be?\nUsing random hyperplane rounding\, a te chnique from semidefinite\noptimization\, Balla\, Janzer\, and Sudakov obt ained a lower bound on\nthis difference in terms of the vector chromatic n umber\, recovering\nknown extremal bounds for $C_r$-free graphs. I will pr esent their\nargument and show that the constant in their vector-chromatic bound is\noptimal by constructing a random sphere graph. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc56d31 DTSTART;TZID=America/Toronto:20261021T100000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261021T110000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi ng-group-quantum-computing-masuda-fatima-maggie SUMMARY:Crypto Reading Group on quantum computing | Masuda Fatima & Maggie\ nSimmons\, Quantum Key Distribution CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Masuda Fatima & Maggie Simmons\n\nAFFILIATION:\n Uni versity of Waterloo\n\nROOM:\n MC 5501\n\nABSTRACT: Quantum Key Distribut ion (QKD) uses the laws of Quantum\nMechanics to allow two parties to prod uce a shared secret key only\nknown to them without it's security relying on the computational\nhardness. In this presentation\, we will introduce t he QKD protocol\nBB84\, and present how it is secure against various attac ks. We will\nalso discuss two major phases in BB84: the information reconc iliation\nphase between keys of sender and receiver via error correcting c odes\nand the privacy amplification phase where two communicating parties\ ndistill highly secret shared key from a larger body of a shared key\,\nwh ich is only partially secret. Finally\, we will give a brief overview\nof Muckle-based hybrid authenticated key exchange (AKE) protocols. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc581cb DTSTART;TZID=America/Toronto:20261022T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261022T153000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an d-enumerative-combinatorics-seminar-patty SUMMARY:Algebraic and Enumerative Combinatorics Seminar | Patty Commins\,\n Signed combinatorics and the Mantaci–Reutenauer algebra CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Patty Commins\n\nAFFILIATION:\n Laboratoire d'Algèb re\, de Combinatoire et d'Informatique\nMathématique (LACIM)\n\nLOCATION: \n MC 5417\n\nABSTRACT: The Mantaci–Reutenauer algebra is a subalgebra of the\ngroup algebra of signed permutations which has close ties to symme tric\nfunctions\, descents\, and characters. In this talk\, we explore its \nrepresentation theory and explain how it is governed by simple\noperatio ns on signed versions of classical combinatorial objects (i.e.\npartitions \, necklaces). This builds on a well-studied type A story for\nSolomon's \ "descent algebra\". The representation-theoretic data we will\nconsider in clude the Cartan matrix\, the representation type\, and a\nconjectural Ext -quiver\; we will explain these notions during the talk.\nThis is ongoing joint work with Alice Dell'Arciprete.\n\nTHERE WILL BE A PRE-SEMINAR PRESE NTING RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTING AT 1: 30PM IN MC 5417. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc59918 DTSTART;TZID=America/Toronto:20261023T153000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261023T163000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq uium-sepehr-assadi-greedy-optimal-semi-streaming SUMMARY:Tutte Colloquium | Sepehr Assadi\, Greedy is Optimal for the\nSemi- Streaming Matching Problem CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Sepehr Assadi\n\nAFFILIATION:\n University of Waterl oo\n\nLOCATION:\n MC 5501\n\nABSTRACT: We prove that no single-pass semi-s treaming algorithm\n(deterministic or randomized) can achieve a better-tha n-half\napproximation to the maximum matching problem. This implies the\no ptimality of the naive greedy algorithm\, answering a longstanding\nopen q uestion in graph streaming literature since the introduction of\nthe model . Our proof consists of two main parts:\n\n 1. Blueprint framework: reduc ing the problem of proving lower bounds\nfor semi-streaming matching to co nstructing certain combinatorial\nobjects which we call blueprints\; and\, \n\n 2. Blueprint construction: an optimal construction of such\nblueprin ts usable within this framework.\n\n Putting these two parts together imp lies our semi-streaming matching\nlower bound.\n\nBased on joint work with Max Jiang and Mars Xiang in\nhttps://arxiv.org/abs/2607.14644 (STOC 2026) and\nhttps://arxiv.org/abs/2607.14656 (arXiv\; July 2026) DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc5abcc DTSTART;TZID=America/Toronto:20261005T110000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261005T120000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combopt-read ing-group-kanstantsin-pashkovich-nearly-tight SUMMARY:CombOpt Reading Group | Kanstantsin Pashkovich\, Nearly Tight Upper \nBound for Matroid Intersection Prophet Inequality CLASS:PUBLIC DESCRIPTION:SPEAKER:\n\nKanstantsin Pashkovich\n\nAFFILIATION:\n University of Waterloo\n\nROOM:\n MC 6029\n\nABSTRACT: In this talk\, I will go ove r the construction that shows a\nlower bound of d/log(d) for the prophet i nequality\, where the feasible\nset is the intersection of d matroids. Thi s talk is based on the paper\n\"A Nearly Tight Lower Bound for Matroid Int ersection Prophet\nInequalities\" by Dimitris Fotakis\, Charalampos Platan os\, Thanos\nTolias. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc5ba71 DTSTART;TZID=America/Toronto:20261009T153000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261009T163000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/tutte-colloq uium-jake-doliskani-quantum-money-wiesner SUMMARY:Tutte Colloquium | Jake Doliskani\, Quantum Money: From Wiesner to\ nStandard Assumptions CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Jake Doliskani\n\nAFFILIATION:\n McMaster University \n\nLOCATION:\n MC 5501\n\nABSTRACT: Quantum money is one of the earlies t ideas in quantum\ncryptography: a banknote is represented by a quantum s tate that cannot\nsimply be copied. Wiesner’s original proposal required the bank to\nverify every transaction\, motivating the notion of public-k ey quantum\nmoney\, where anyone can verify a banknote while only the bank can\ncreate new ones.\n\nIn this talk\, I will trace the story of quantum money from Wiesner’s\nscheme\, through the hidden-subspace construction of Aaronson and\nChristiano\, to Zhandry’s recent construction from abe lian group\nactions. I will discuss why previous proposals were either bro ken or\nrelied on non-standard assumptions\, and then present recent work\ nshowing that Zhandry’s construction can be based\, in the generic\ngrou p-action model\, on the standard group-action discrete logarithm\nassumpti on. I will conclude with the main idea behind the security\nproof. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc5cc1d DTSTART;TZID=America/Toronto:20261007T100000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261007T110000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi ng-group-quantum-computing-mojtaba-fadavi-and SUMMARY:Crypto Reading Group on quantum computing | Mojtaba Fadavi and Taha \nHedayat\, Quantum Circuits CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Mojtaba Fadavi & Taha Hedayat\n\nAFFILIATION:\n Univ ersity of Waterloo\n\nROOM:\n MC 5501\n\nABSTRACT: Equipped with the know ledge of quantum information\, we\npresent how to use quantum states to bu ild a quantum algorithm. While\nclassical circuits represent how one makes algorithms using the bits 0\nand 1\, quantum circuits represent how one m akes algorithms using\nqubits $\\ket{\\alpha} = \\alpha_0 \\ket{0} + \\alp ha_1\\ket{1}$. In this\npresentation\, we will introduce the definition an d presentation of\nquantum gates. Starting with 1-qubit gates and expandin g to n-qubit\ngates. We also present the standard gates such as the Pauli Gates\,\nCNOT\, CCNOT\, SWAP\, etc. Then we proceed to see the effects and \ninteractions of these gates along with some measurements. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc5e753 DTSTART;TZID=America/Toronto:20261008T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261008T153000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an d-enumerative-combinatorics-seminar-jun-yan SUMMARY:Algebraic and Enumerative Combinatorics Seminar | Jun Yan\, Exact\n enumeration of lozenge tilings of a triangular region CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Jun Yan\n\nAFFILIATION:\n University of Waterloo\n\n LOCATION:\n MC 5417\n\nABSTRACT: Tiling enumerations problems have fascin ating connections\nwith many other combinatorial problems involving perfec t matchings\,\nlattice paths\, and determinants. In this talk\, I will bri efly survey\nsome of the classical results and methods in this area. Then\ , I will\npresent a new result enumerating lozenge tilings of a triangular \nregion. Interestingly\, the formula\, reminiscent of the famous\nKastele yn formula counting domino tilings of the rectangle\, contains\nroots of u nity and does not obviously output an integer.\n\nTHERE WILL BE A PRE-SEMI NAR PRESENTING RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEVEL START ING AT 1:30PM. DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc5faea DTSTART;TZID=America/Toronto:20261005T150000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20261005T160000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/graphs-and-m atroids-jun-yan-ramsey-numbers-trees SUMMARY:Graphs and Matroids | Jun Yan\, Ramsey numbers of trees CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Jun Yan\n\nAFFILIATION:\n University of Waterloo\n\n ROOM:\n MC 6029\n\nABSTRACT: Let T be a tree with bipartition class sizes t_1>=t_2.\nMotivated by two simple lower bound constructions\, Burr conje ctured\nthat the Ramsey number of T\, denoted by R(T)\, is exactly\nmax{t_ 1+2t_2\,2t_1}-1. While this conjecture turns out to be false\, all\nknown counterexamples have large maximum degrees. In a joint work with\nRichard Montgomery and Matías Pavez-Signé\, we show that there exists\na constan t c>0\, such that Burr's conjecture does hold if T has maximum\ndegree at most c(t_1+t_2). In particular\, this determines the exact\nRamsey numbers of a large family of trees. In this talk\, I will go\nover some backgroun d on tree embeddings\, and give an overview of our\nproof.  DTSTAMP:20261019T190116Z END:VEVENT BEGIN:VEVENT UID:6ad668fc61172 DTSTART;TZID=America/Toronto:20260930T100000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20260930T113000 URL:https://uwaterloo.ca/combinatorics-and-optimization/events/combinatoric s-and-optimization-reading-group-resolution-0 SUMMARY:Combinatorics and Optimization reading group | Resolution of Matroi d\nSecretary Conjecture - Day 2 CLASS:PUBLIC DESCRIPTION:SPEAKER:\n Kanstantsin Pashkovich\n\nAFFILIATION:\n University of Waterloo\n\nROOM:\n MC 6029\n\nABSTRACT: I will go over the recent pap er by Sahil Singla proving\nMatroid Secretary Conjecture. DTSTAMP:20261019T190116Z END:VEVENT END:VCALENDAR