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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:69e21f8da2d66
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:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8da778d
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:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8da8cc4
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:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8daa5a1
DTSTART;TZID=America/Toronto:20260417T103000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260417T113000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-maggie-simmons-formally-verified
SUMMARY:Crypto Reading Group - Maggie Simmons-Formally Verified Correctness
 \nBounds for Lattice-Based Cryptography
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Maggie Simmons\n\nAFFILIATION:\n University of Wat
 erloo\n\nLOCATION:\n MC 6029\n\nABSTRACT:\n\nDecryption errors play a cruc
 ial role in the security of KEMs based on\n\nFujisaki-Okamoto because the 
 concrete security guarantees provided by \nthis transformation directly de
 pend on the probability of such an\nevent \nbeing bounded by a small real 
 number. In this paper we present an \napproach to formally verify the clai
 ms of statistical probabilistic \nbounds for incorrect decryption in latti
 ce-based KEM constructions.\nOur \nmain motivating example is the PKE encr
 yption scheme underlying\nML-KEM. \nWe formalize the statistical event tha
 t is used in the literature to \nheuristically approximate ML-KEM decrypti
 on errors and confirm that\nthe \nupper bounds given in the literature for
  this event are correct. We \nconsider FrodoKEM as an additional example\,
  to demonstrate the wider \napplicability of the approach and the verifica
 tion of a correctness \nbound without heuristic approximations. We also di
 scuss other \n(non-approximate) approaches to bounding the probability of 
 ML-KEM \ndecryption.
DTSTAMP:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8dab9c3
DTSTART;TZID=America/Toronto:20260409T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260409T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-mahrud-0
SUMMARY:Algebraic and Enumerative combinatorics seminar - Mahrud\nSayrafi-C
 onstructing exceptional collections for toric varieties
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Mahrud Sayrafi\n\nAFFILIATION:\n McMaster University
 \n\nLOCATION:\n MC 5417\n\nABSTRACT: Exceptional collections are a powerf
 ul tool for\nunderstanding the derived category of coherent sheaves on alg
 ebraic\nvarieties\, with applications in commutative algebra\, birational\
 ngeometry\, and mirror symmetry. While the existence of exceptional\ncolle
 ctions is known for classical varieties such as Grassmannians and\nflag va
 rieties\, constructing explicit collections for toric varieties\npresents 
 challenges in combinatorial algebraic geometry. In this talk\nI will descr
 ibe a computational approach to constructing full strong\nexceptional coll
 ections consisting of complexes of line bundles for\ntoric varieties. No b
 ackground in derived categories is assumed.\n\nTHERE WILL BE A PRE-SEMINAR
  PRESENTING RELEVANT BACKGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTING
  AT 1:30PM.
DTSTAMP:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8dacfe9
DTSTART;TZID=America/Toronto:20260410T103000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260410T113000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/crypto-readi
 ng-group-elnaz-hessami-pilehrood-shadowfax
SUMMARY:Crypto Reading Group - Elnaz Hessami Pilehrood-Shadowfax: Hybrid\nS
 ecurity and Deniability for AKEMs
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Elnaz Hessami Pilehrood\n\nAFFILIATION:\n Universi
 ty of Waterloo\n\nLOCATION:\n MC 6029\n\nABSTRACT:As cryptographic protoco
 ls transition to post-quantum\nsecurity\, most adopt hybrid solutions comb
 ining classical and\npost-quantum assumptions. This shift often sacrifices
  efficiency\,\ncompactness\, or even security. One such property is deniab
 ility\, which\nenables users to plausibly deny authorship of potentially\n
 incriminating messages. While classical protocols like X3DH key\nagreement
  (used in Signal and WhatsApp) provide deniability\,\npost-quantum protoco
 ls like PQXDH and Apple’s iMessage with PQ3 do\nnot. This work addresses
  this gap by investigating how to efficiently\npreserve deniability in pos
 t-quantum protocols. Specifically\, we\npropose two hybrid schemes for aut
 henticated key encapsulation\nmechanisms (AKEMs). The first is a black-box
  construction that\npreserves deniability when both constituent AKEMs are 
 deniable. The\nsecond is Shadowfax\, a non-black-box AKEM that achieves hy
 brid\nsecurity\, integrating a classical non-interactive key exchange\, a\
 npost-quantum key encapsulation mechanism\, and a post-quantum ring\nsigna
 ture. Shadowfax satisfies deniability in both dishonest and\nhonest receiv
 er settings\, relying on statistical security in the\nformer and on a sing
 le pre- or post-quantum assumption in the latter.\nFinally\, we provide se
 veral portable implementations of Shadowfax.\nWhen instantiated with stand
 ardised components (ML–KEM and Falcon)\,\nShadowfax yields ciphertexts o
 f 1 728 bytes and public keys of 2 036\nbytes\, with encapsulation and dec
 apsulation costs of 1.8M and 0.7M\ncycles on an Apple M1 Pro.
DTSTAMP:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8dae0cd
DTSTART;TZID=America/Toronto:20260406T144500
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260406T154500
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/graphs-and-m
 atroids-eileen-robinson-coloring-claw-free
SUMMARY:Graphs and Matroids - Eileen Robinson-Coloring claw-free graphs of\
 nbounded codegree
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Eileen Robinson\n\nAFFILIATION:\n Université libre 
 de Bruxelles\n\nROOM:\n MC 5479\n\nABSTRACT:We define the codegree of a gi
 ven graph as the maximum number\nof neighbors that any two distinct vertic
 es have in common.\n\nIn 2002\, V. Vu proposed that for a given graph\, it
 s chromatic number\nshould never be too much larger than its codegree\, pr
 ovided that its\ncodegree is not too small as a proportion of its maximum 
 degree.
DTSTAMP:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8daf0f3
DTSTART;TZID=America/Toronto:20260407T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260407T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-ashleigh
SUMMARY:Algebraic and enumerative combinatorics seminar-Ashleigh\nAdams-Pro
 motion\, plane partitions\, partial evaluations\, and webs
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Ashleigh Adams\n\nAFFILIATION:\n North Dakota State 
 University\n\nLOCATION:\n MC 6029\n\nABSTRACT: Webs are graphical objects
  that give a tangible\,\ncombinatorial way to compute and classify tensor 
 invariants. Recently\,\nGaetz\, Pechenik\, Pfannerer\, Striker\, and Swans
 on (arXiv:2306.12501)\nfound a rotation-invariant web basis for SL₄\, as
  well as its quantum\ndeformation U_q(sl₄)\, and a bijection between mov
 e equivalence\nclasses of SL₄-webs and fluctuating tableaux such that we
 b rotation\ncorresponds to tableau promotion. They also found a bijection 
 between\nthe set of plane partitions in an a×b×c box and a benzene move\
 nequivalence class of SL₄-webs by determining the corresponding\noscilla
 ting tableau. In this talk\, I will similarly find the\noscillating tablea
 ux corresponding to plane partitions in certain\nsymmetry classes by chara
 cterizing them via certain lattice words. A\ndynamical action on tableaux\
 , called promotion\, corresponds to\nrotation of SL₄-webs. I will show h
 ow promotion of certain\nsubtableaux aligns with rotation of their respect
 ive webs. I will also\nshow that this correspondence maps through a projec
 tion to either\nSL₂ or SL₃ webs. Moreover\, this projection is exactly
  a partial\nevaluation of webs. This talk will be given through the lens o
 f the\ncombinatorics of webs and tableaux. Some of this work is joint with
 \nJessica Striker.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTING RELEVANT BAC
 KGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTING AT 1:30PM.
DTSTAMP:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8db03b1
DTSTART;TZID=America/Toronto:20260330T123000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260330T133000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/co-reading-g
 roup-jacob-skitsko-simple-proof-hardness-matrix
SUMMARY:C&O Reading Group - Jacob Skitsko-A Simple Proof of Hardness of Mat
 rix\nCompletion
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n\n Jacob Skitsko\n\nAFFILIATION:\n University of Wate
 rloo\n\nLOCATION:\n MC 6029\n\nABSTRACT:\n\nIn the matrix completion probl
 em\, we are given an incomplete matrix A\nas input. Some entries are fille
 d in\, and some entries have the value\n\"*\". Our task is to fill in the 
 \"*\" entries so that the resulting\ncompleted matrix has minimum rank. We
 'll discuss a simple proof from\nShitov showing that it is hard to disting
 uish between an incomplete\nmatrix having a rank 3 completion\, or all com
 pletions requiring at\nleast rank 4. \nThe idea is to index the matrix by 
 vectors. These vectors will\nrepresent a circuit computing a family of pol
 ynomials\, f(x) in F. The\nhope is that any rank 3 completion will be forc
 ed to fill in the\nmatrix values according to these vector labels. Thus\, 
 the completion\nwill specify values for x_i\, x_j\, x_i + x_j\, x_i * x_j\
 , ... \, and so\non until it specifies values for our polynomials f(x). If
  we force the\nf(x) in F entries to be 0\, then this is exactly a solution
  to the\npolynomial system F. Seeing why any rank 3 completion should be f
 orced\nto operate in this way takes a bit of squinting\, but is overall qu
 ite\npleasant.
DTSTAMP:20260417T115453Z
END:VEVENT
BEGIN:VEVENT
UID:69e21f8db13e7
DTSTART;TZID=America/Toronto:20260402T143000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260402T153000
URL:https://uwaterloo.ca/combinatorics-and-optimization/events/algebraic-an
 d-enumerative-combinatorics-seminar-hadleigh
SUMMARY:Algebraic and enumerative combinatorics seminar - Hadleigh\nFrost-N
 ested nestings\, Moment-Cumulant relations and the Combinatorics\nof the C
 osmos
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Hadleigh Frost\n\nAFFILIATION:\n Institute for Advan
 ced Study\n\nLOCATION:\n MC 5417\n\nABSTRACT: Cosmological correlation fu
 nctions probe the quantum\norigins of structure in the universe and are a 
 prototype for many\ncalculations in physics. I will share recent work on t
 he complexes\,\nfans and polytopes associated to these functions based on\
 narXiv:2602.21194 and ongoing work. Two structures lie at the heart of\nth
 is story: (1) incidence relations between chains and anti-chains\,\n(2) a 
 notion of \"nested sets of nested sets\". Both structures can be\nstudied 
 for an arbitrary lattice\, but building sets of the boolean\nlattice are m
 y main motivation.\n\nTHERE WILL BE A PRE-SEMINAR PRESENTING RELEVANT BAC
 KGROUND AT THE\nBEGINNING GRADUATE LEVEL STARTING AT 1:30PM.
DTSTAMP:20260417T115453Z
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