Codes and Expansions (CodEx) Seminar

An international remote seminar on the theory and applications of harmonic analysis, combinatorics, and algebra.

Tuesdays at 10 a.m. PDT / 1 p.m. EDT / 5 p.m. UTC / 7 p.m. CEST

Zoom. To access the Zoom link, please join the mailing list by entering your information here.

Recorded talks are on our YouTube channel.

Organized by:
Joey Iverson (Iowa State University)
John Jasper (Air Force Institute of Technology)
Emily J. King (Colorado State University)
Dustin Mixon (The Ohio State University)

Upcoming talks:

July 2, 2024[Summer Student and Postdoc Talks] Hannah Friedman (UC Berkeley):
July 9, 2024[Summer Student and Postdoc Talks] Chad Berner (Iowa State University):
July 16, 2024[Summer Student and Postdoc Talks] George Kevrekidis (Johns Hopkins):
July 23, 2024[Summer Student and Postdoc Talks] Enrique Alvarado (UC Davis / Iowa State University):
July 30, 2024[Summer Student and Postdoc Talks] Enrique Gomez-Leos (Iowa State University):
Sarah McCarty (Iowa State University):

Past talks:

May 14, 2024 Joey Iverson (Iowa State University): "The optimal arrangement of 2d lines in C^d" Abstract
May 7, 2024 Ole Christensen (Technical University of Denmark): "Frames and redundancy" Abstract| Video
April 23, 2024 Nathaniel Johnston (Mount Allison University): "A New Formula for the Determinant" Abstract | Video
April 16, 2024 Mátyás Domokos (Alfréd Rényi Institute of Mathematics): "Degree bounds for separating invariants" Abstract | Video
April 2, 2024 Jonathan D.H. Smith (Iowa State University) "Codes, Errors, and Loops" Abstract | Video
March 26, 2024 Elizabeth Munch (Michigan State University) "Comparing Embedded Shapes Using Topological Summaries" Abstract | Video
March 19, 2024 Demetrio Labate (University of Houston) "Provable approximations of multivariate functions on smooth manifolds using deep ReLU neural networks" Abstract | Video
March 5, 2024 Joe Kileel (University of Texas at Austin): "Covering Number of Real Algebraic Varieties and Beyond" Abstract | Video
February 27, 2024 Samuel Ballas (Florida State University) "Frame theory for vector bundles" Abstract | Video
February 20, 2024 Abiy Tasissa (Tufts University) "A dual basis approach to classical multidimensional scaling" Abstract | Video
February 13, 2024 Joseph Thomas Iosue (University of Maryland) "Projective toric designs, difference sets, and quantum state designs" Abstract | Video
February 6, 2024 Francesca Bartolucci (TU Delft): "A Tour in Wavelet Phase Retrieval" Abstract | Video
January 30, 2024 Oscar Mickelin (Princeton University): "A fast algorithm for Fourier-Bessel expansions" Abstract | Video
January 23, 2024 Edinah Koffi Gnang (Johns Hopkins University): "From graph decomposition to matrix apportionment and back" Abstract
December 5, 2023 Hannah Lawrence (MIT): "Learning Polynomial Problems with SL(2,R)-Equivariance" Abstract | Video
November 14, 2023 Michael Catanzaro (Geometric Data Analytics, Inc.): "Topological Parallax: A Geometric Specification for Deep Perception Models" Abstract | Video
November 7, 2023 Daniel Freeman (St Louis University): "Recovering vectors from saturated measurements" Abstract | Video
October 31, 2023 Sylvester Eriksson-Bique (University of Jyväskylä): "BiLipschitz Embeddings of Manifolds, Orbifolds and Metric Spaces" Abstract | Video
October 24, 2023 Ben Blum-Smith (Johns Hopkins University): "Estimating a signal corrupted by a cyclic group action plus noise" Abstract | Video
October 17, 2023 Shira Faigenbaum-Golovin (Duke University): "Can We Approximate It? Manifolds, Refinable Functions, and the Approximation Power of Neural Networks" Abstract | Video
October 10, 2023 Dan Edidin (University of Missouri): "The second moment and the sparse multi-reference alignment problem" Abstract | Video
October 3, 2023 Courtney Paquette (McGill University): "Hitting the High-D(imensional) Notes: An ODE for SGD learning dynamics in high-dimensions" Abstract | Video
September 26, 2023 Mark Iwen (Michigan State): "Sparse Spectral Methods for Solving High-Dimensional and Multiscale Elliptic PDEs" Abstract | Video
September 19, 2023 Robert Webber (Caltech): "Rocket-propelled Cholesky: Addressing the challenges of large-scale kernel computations" Abstract | Video
September 12, 2023 Steven Gortler (Harvard University): "Invariant Embeddings" Abstract | Video
August 22, 2023[Summer Student and Postdoc Talks]
Efstratios Tsoukanis (University of Maryland): "Coorbit Invariant Embeddings" Abstract | Video
August 15, 2023[Summer Student and Postdoc Talks]
Daniel Packer (The Ohio State University): "Max Filtering with Reflection Groups" Abstract | Video
August 8, 2023[Summer Student and Postdoc Talks]
Arun Suresh (University of Missouri): "On the Generic Crystallographic Phase Retrieval Problem" Abstract | Video
August 1, 2023[Summer Student and Postdoc Talks]
Christopher Dock (Tufts University): "Instability of Quantum Tomography with Bounded Operators" Abstract | Slides | Video
July 25, 2023[Summer Student and Postdoc Talks]
David Bartusel (RWTH Aachen): "The role of connectedness in STFT phase retrieval" Abstract | Video
July 18, 2023[Summer Student and Postdoc Talks]
Keenan Eikenberry (Arizona State University): "Markov Kernels Valued in Wasserstein Spaces" Abstract | Video
July 11, 2023[Summer Student and Postdoc Talks]
Mitchell Taylor (UC Berkeley): "Stable phase retrieval in function spaces" Abstract | Video
June 27, 2023[Summer Student and Postdoc Talks]
Pu-Ting Yu (Georgia Tech): "Convergence of Frame Series" Abstract | Video
June 22, 2023[Summer Student and Postdoc Talks]
Donggeun Ryou (University of Rochester): "Near-Optimal Restriction Estimates for Cantor Sets on the Parabola" Abstract | Video
June 14, 2023[Summer Student and Postdoc Talks]
Dylan Domel-White (Vanderbilt University): "Algorithms and Guarantees for One-bit Phase Retrieval" Abstract | Video
June 6, 2023[Summer Student and Postdoc Talks]
Marc Christian Zimmermann (University of Cologne): "Critical lattices in the Gaussian core model" Abstract | Video
May 30, 2023[Summer Student and Postdoc Talks]
Josue Tonelli-Cueto (University of Texas San Antonio / Johns Hopkins University): "Condition Numbers and Probability for Explaining Algorithms" Abstract | Video
May 2, 2023Jakob Lemvig (Technical University of Denmark - DTU): "The Gabor frame set problem for Hermite functions" Abstract | Video
April 25, 2023James Murphy (Tufts University): "Intrinsically Low-Dimensional Models for Wasserstein Space: Geometry, Statistics, and Learning" Abstract | Video
April 18, 2023Margaret Cheney (Colorado State University): "Tuning to Target Resonances" Abstract | Video
April 11, 2023Shahaf Nitzan (Georgia Tech): "A set with no Riesz basis of exponentials" Abstract
April 4, 2023Bill Martin (Worcester Polytechnic Institute): "Quantum isomorphic graphs from association schemes" Abstract | Video
March 28, 2023Dustin G. Mixon (The Ohio State University): "Bilipschitz invariants" Abstract | Video
March 21, 2023Rachel Greenfeld (Institute for Advanced Study, Princeton): "The structure of translational tilings" Abstract
March 7, 2023Krystal Guo (University of Amsterdam and QuSoft): "Strongly regular graphs with a regular point" Abstract | Video
February 28, 2023Judith Packer (University of Colorado Boulder): "Wavelets coming from representations of graph C*-algebras" Abstract | Slides | Video
February 21, 2023Nadav Dym (Technion): "Efficient Invariant Embeddings for 3D point sets" Abstract | Video
February 14, 2023Alhussein Fawzi (Google DeepMind): "Discovering faster matrix multiplication algorithms with deep reinforcement learning" Abstract | Video
February 7, 2023Ursula Molter (Universidad de Buenos Aires): "Best 'good' subspace data fitting" Abstract | Video
January 31, 2023Ingemar Bengtsson (Stockholm University): "Pythagorean SICs" Abstract | Video
January 24, 2023Oleg Musin (University of Texas Rio Grande Valley) "Majorization and optimal spherical configurations" Abstract | Video
January 17, 2023Stefan Steinerberger (University of Washington): "Graphical Designs" Abstract | Slides | Video
December 6, 2022Bernhard Bodmann (University of Houston): "Spotting irregularities with reaction and diffusion: A scattering transform on graphs and extremes in log-normal random walks" Abstract | Video
November 29, 2022Tom Needham (Florida State University): "Symplectic Geometry and Fusion Frames" Abstract | Video
November 15, 2022Felix Voigtländer (Catholic University Eichstätt-Ingolstadt): "Sampling numbers of the Fourier-type Barron spaces" Abstract | Video
November 8, 2022Andreas Heinecke (Yale-NUS College): "Unsupervised statistical learning in ancient economic history" Abstract | Video
November 1, 2022Carlos Cabrelli (University of Buenos Aires): "Frames by Orbits of Operators and Model Spaces" Abstract | Video
October 25, 2022Kiyoto Yoshino (Tohoku University): "The Lemmens-Seidel conjecture for base size 5" Abstract | Video
October 18, 2022Doug Cochran (Arizona State University): "Geometry of Invariants for Generalized Coherence Tests" Abstract | Video
October 11, 2022Danylo Yakymenko (Institute of Mathematics of NAS of Ukraine): "On the continuous Zauner conjecture" Abstract | Video | Slides
October 4, 2022Dardo Goyeneche (Universidad de Antofagasta): "Mutually unbiased frames" Abstract | Video | Slides
September 27, 2022Pete Casazza (University of Missouri): "Piecewise Scalable Frames" Abstract | Video
September 20, 2022Travis Russell (Dartmouth College): "Quantum correlations via Operator Systems" Abstract | Video
September 6, 2022Michael Perlmutter (University of California Los Angeles): "Group Invariant Scattering on Graphs, Manifolds, and Other Measure Spaces" Abstract | Video | Slides
August 30, 2022John Jasper (Air Force Institute of Technology): "Equi-isoclinism from symmetry" Abstract | Slides | Video
August 23, 2022Jameson Cahill (University of North Carolina at Wilmington): "Max filtering" Abstract | Video
August 16, 2022[Summer Student and Postdoc Talks]
Matthias Wellershoff (University of Maryland): "Uniqueness of phase retrieval from sampled Gabor measurements: a short overview" Abstract | Video
August 9, 2022[Summer Student and Postdoc Talks]
Vicky Kouni (University of Athens): "Analysis Compressed Sensing: from Model-Based Methods to Deep Unfolding Networks" Abstract | Video
July 19, 2022[Summer Student and Postdoc Talks]
Victor Bailey (Georgia Tech) "Frames via Unilateral Iterations of Bounded Operators" Abstract | Video
July 12, 2022[Special Session on Recent Advances in Packing]
Shujie Kang (University of Texas at Arlington): "Non-informationally complete Gabor POVMs" Abstract | Video
July 5, 2022[Special Session on Recent Advances in Packing]
Shuxing Li (Simon Fraser University): "Packings of Partial Difference Sets" Abstract | Video
June 28, 2022[Summer Student and Postdoc Talks]
Simon Ruetz (Universität Innsbruck): "Adapted variable density subsampling for compressed sensing" Abstract | Video
June 21, 2022[Special Session on Recent Advances in Packing]
Xinyu (Norah) Tan (Duke University): "Quadratic Form Diagonal Gates and Grassmannian Packings" Abstract | Video
Zilin Jiang (Arizona State University): "Forbidden subgraphs and spherical two-distance sets" Abstract | Video
June 14, 2022[Special Session on Recent Advances in Packing]
Dustin G. Mixon (The Ohio State University): "An Approximate Positivstellensatz" Abstract | Video
Kasso Okoudjou (Tufts University): "Minimizing the p-frame potentials" Abstract | Video
June 7, 2022[Special Session on Recent Advances in Packing]
Gary Greaves (Nanyang Technological University): "Hermitian matrices of roots of unity and their characteristic polynomials" Abstract | Video
Matt Fickus (Air Force Institute of Technology): "Harmonic Grassmannian codes" Abstract | Video
May 31, 2022[Special Session on Recent Advances in Packing]
Emily J. King (Colorado State University): "The Combinatorics of Equiangular Tight Frame Substructures" Abstract | Video
Alexander Barg (University of Maryland): "Bounds for the sum of distances of spherical sets of small size" Abstract | Video
May 24, 2022[Special Session on Recent Advances in Packing]
Gene Kopp (Purdue University/Louisiana State University): "A step toward a constructive proof of Zauner's conjecture" Abstract | Video
May 3, 2022Amit Singer (Princeton University): "Method of moments in cryo-electron microscopy" Abstract | Video
April 26, 2022Doug Hardin and Nate Tenpas (Vanderbilt University): "Linear programming bounds for discrete periodic energy problems" Abstract | Video
April 19, 2022Deanna Needell (University of California Los Angeles): "Online nonnegative matrix factorization and applications" Abstract | Video
April 12, 2022Hau-Tieng Wu (Duke University): "Some recent progress in diffusion based manifold learning and its applications" Abstract | Video
April 5, 2022Simon Foucart (Texas A&M University): "Integrating Observation Errors in Optimal Recovery" Abstract
March 29, 2022Felix Krahmer (Technische Universität München): "The convex geometry of blind deconvolution revisited" Abstract | Video
March 22, 2022Soledad Villar (Johns Hopkins University): "Equivariant machine learning and dimensional analysis" Abstract | Video
March 15, 2022Sinan Gunturk (New York University): "Approximation with one-bit polynomials and one-bit neural networks" Abstract | Video
March 8, 2022Igor Balla (Hebrew University of Jerusalem): "Equiangular lines and regular graphs" Abstract | Video
March 1, 2022Jonathan Jedwab (Simon Fraser University): "Perfect sequence covering arrays" Abstract | Slides | Video
February 22, 2022Sho Suda (National Defense Academy of Japan) "Two topics on equiangular tight frames" Abstract | Video
February 15, 2022Tim Kunisky (Yale University): "Dual bounds for the positive definite functions approach to mutually unbiased bases" Abstract | Video
February 8, 2022Darrin Speegle (Saint Louis University): "Simultaneous Dilation and Translation Tilings of R^n" Abstract | Video
February 1, 2022Henry Adams (Colorado State University): "The topology of projective codes" Abstract | Slides | Video
January 25, 2022Lutz Warnke (University of California San Diego): "The Density of Costas Arrays Decays Exponentially" Abstract | Video
January 18, 2022Bernd Sturmfels (University of California Berkeley and Max Planck Institute for Mathematics in the Sciences Leipzig): "Linear PDE with Constant Coefficients" Abstract | Slides
December 7, 2021Rima Alaifari (ETH Zürich): "(Non-)uniqueness of phase recovery from Gabor and wavelet transform measurements" Abstract | Video
November 30, 2021Dan Edidin (University of Missouri): "Dihedral multi-reference alignment" Abstract | Video | Slides
November 16, 2021Wojciech Czaja (University of Maryland): "Fourier Scattering as Efficient Feature Extraction" Abstract | Video
November 9, 2021Monika Dörfler (Universität Wien): "Structure and Effective Dimensionality of Time Series Data Sets" Abstract
November 2, 2021Alexander Powell (Vanderbilt University): "Dynamical Duals and Error Diffusion" Abstract
October 26, 2021Markus Grassl (International Centre for Theory of Quantum Technologies, University of Gdańsk): "Computing SIC-POVMs using Permutation Symmetries and Stark Units" Abstract | Video | Slides
October 19, 2021Joey Iverson (Iowa State University): "Equiangular lines over finite fields" Abstract | Video | Slides
October 12, 2021Clay Shonkwiler (Colorado State University): "A Lie Algebraic Perspective on Frame Theory" Abstract | Video
October 5, 2021X.Y. Han (Cornell University): "Prevalence of Neural Collapse during the terminal phase of deep learning training" Abstract | Video
September 28, 2021Boumediene Et-Taoui (Université de Haute Alsace): "A survey on complex conference matrices" Abstract | Video | Slides
September 21, 2021Naoki Saito (University of California Davis): "Multiscale Graph Basis Dictionaries" Abstract | Video
September 14, 2021Tom Needham (Florida State University): "Applications of Symplectic Geometry to Frame Theory" Abstract | Video | Slides
September 7, 2021Armenak Petrosyan (Georgia Institute of Technology): "Integral neural networks with weight penalization" Abstract | Video
August 31, 2021Mauro Maggioni (Johns Hopkins University): "Learning Interaction laws in particle- and agent-based systems" Abstract | Video
August 24, 2021Longxiu Huang (University of California Los Angeles): "CUR Decompositions and their Applications" Abstract | Video
August 10, 2021Romanos Diogenes-Malikiosis (Aristotle University of Thessaloniki): "Recent developments in the discrete Fuglede conjecture" Abstract | Slides | Video
August 3, 2021Matt Herman (Fourier Genetics): "Fourier Analysis on the Genome" Abstract | Video | Slides
July 27, 2021Nate Strawn (Georgetown University): "3D Filament Plots from Optimally Smooth 2D Andrew's Plots" Abstract | Slides | Video
July 13, 2021[Summer Student and Postdoc Talks]
Davi Castro-Silva (Universität zu Köln): "Geometrical sets with forbidden configurations" Abstract | Video | Slides
July 6, 2021[Summer Student and Postdoc Talks]
Nathan Lindzey (University of Colorado Boulder): "Discrete Harmonic Analysis on Matchings" Abstract | Video
June 29, 2021Xuemei Chen (University of North Carolina Wilmington): "Frame optimization with projective Riesz kernel" Abstract | Video
June 22, 2021[Summer Student and Postdoc Talks]
Nadiia Derevianko (Universität Göttingen): "Estimation of Signal Parameters by Iterative Rational Approximation" Abstract | Video
June 15, 2021Michael Perlmutter (University of California Los Angeles): "Convolutional Networks on (Directed) Graphs via the Graph Fourier Transform" Abstract | Video | Slides
June 8, 2021Mikhail Ganzhinov (Aalto University): "Infinite families of optimal biangular line packings" Abstract | Video
June 1, 2021[Summer Student and Postdoc Talks]
Joseph Cummings (University of Kentucky): "Phylogenetic Networks" Abstract | Video
May 25, 2021Elina Robeva (University of British Columbia): "Orthogonal and Incoherent Tensor decomposition" Abstract | Video
May 18, 2021Radu Balan (University of Maryland):"Embeddings of Metric Spaces induced by Permutation Groups" Abstract | Video
May 11, 2021Steve Butler (Iowa State University): "Hadamard diagonalizable graphs of small order" Abstract | Video
May 4, 2021Cynthia Vinzant (North Carolina State University): "The geometry of spectrahedra" Abstract | Video | Slides
April 27, 2021Azita Mayeli (City University of New York, the Graduate Center): "Exponential completeness and φ-approximate orthogonality on the unit ball" Abstract
April 20, 2021Marcin Bownik (University of Oregon): "Multiplication-invariant operators and the classification of abelian group frames" Abstract | Video | Slides
April 13, 2021Gary Greaves (Nanyang Technological University): "Real equiangular line systems in low dimensions" Abstract | Video | Slides
April 6, 2021Robert Calderbank (Duke University): "Coherent Noise" Abstract |
March 30, 2021Vignon Oussa (Bridgewater State University): "Why are topics such as differential geometry and representation theory useful to frame theory?" Abstract | Video
March 23, 2021Zilin Jiang (Arizona State University): "Spherical two-distance sets and spectral theory of signed graphs" Abstract " Video
March 16, 2021Daniel Freeman (St Louis University): "Discretizing L_p norms" Abstract | Video
March 9, 2021Keaton Hamm (The University of Texas at Arlington): "Column Selection and You" Abstract | Video
March 2, 2021Ram Zamir (Tel Aviv University): "Asymptotic Frame Theory for Analog Coding" Abstract | Video | Slides
February 23, 2021Joshua A. Grochow (University of Colorado Boulder): "Codes and Expansions in Algorithms for Matrix Multiplication" Abstract | Video | Slides
February 16, 2021Karin Schnass (Universität Innsbruck): "Random submatrices with non-uniformly distributed supports" Abstract | Video
February 9, 2021Eugenio Hernández (Universidad Autónoma de Madrid): "Spaces invariant under unitary representations and the bracket" Abstract | Slides | Video
February 2, 2021Emily J. King (Colorado State University): "A Potpourri of Projective 2-Designs" Abstract | Video | Slides
January 26, 2021Steven Flammia (AWS Center for Quantum Computing): "Ghosts, Necromancy, and Zauner's Conjecture" Abstract | Video
December 8, 2020Chris Heil (Georgia Tech): "Frames, Erasures, and Excess in Infinite Dimensions" Abstract | Video | Slides
December 1, 2020Hartmut Führ (RWTH Aachen): "Frames of translates and the bandwidth intuition" Abstract | Video | Slides
November 17, 2020Philipp Petersen (Universität Wien): "Functions with structured singularities" Abstract | Video
November 10, 2020Alex Cloninger (University of California at San Diego): "Fast Statistical and Geometric Distances Between Families of Distributions" Abstract | Video
November 3, 2020Gerlind Plonka-Hoch (Universität Göttingen): "Optimal Rank-1 Hankel Approximation of Matrices" Abstract | Video | Slides
October 27, 2020Akram Aldroubi (Vanderbilt University): "Transport transforms for data analysis and machine learning" Abstract | Video
October 20, 2020Dustin G. Mixon (The Ohio State University): "Symmetry and optimality in codes" Abstract | Video
October 13, 2020John J. Benedetto (University of Maryland): "Spectral super-resolution and unique extensions for complex measures" Abstract | Video
October 6, 2020Shahaf Nitzan (Georgia Tech): "A few remarks on 'good' exponential Riesz bases" Abstract
September 29, 2020Boris Bukh (Carnegie Mellon University): "Ranks of matrices with few distinct entries" Abstract | Video
September 22, 2020Eric Weber (Iowa State University): "Conjugate Phase Retrieval in Paley-Wiener Space" Abstract | Video | Slides
September 15, 2020Bill Martin (Worcester Polytechnic Institute): "Schoenberg's Theorem and Association Schemes" Abstract | Video | Slides
September 8, 2020Hanmeng (Harmony) Zhan (York University): "DRACKNs and their applications in quantum information" Abstract | Video
September 1, 2020Chris Manon (University of Kentucky): "Spaces of Eigenvalues" Abstract | Video
August 25, 2020Frank Vallentin (Universität zu Köln): "Coloring the Voronoi tessellation of lattices" Abstract | Video
August 18, 2020David Gross (Universität zu Köln): "Representation theory of the Clifford group, with sundry applications" Abstract | Video
August 11, 2020Kasso Okoudjou (Tufts University): "The search for universal minimizers of p-frame potentials" Abstract | Video
August 4, 2020 Marcus Appleby (University of Sydney): "SICs and Number Theory" Abstract | Video
July 28, 2020Matt Fickus (Air Force Institute of Technology): "Mutually Unbiased Equiangular Tight Frames" Abstract | Slides | Video
July 21, 2020Vern Paulsen (University of Waterloo): "Entanglement Breaking Maps and Zauner's Conjecture" Abstract | Video
July 14, 2020Afonso S. Bandeira (ETH Zürich): "Hardness of refuting coloring in random graphs and quiet computational planting" Abstract | Video
July 7, 2020Bernhard Bodmann (University of Houston): "Polynomial embeddings as cheat codes for a real Game of Sloanes" Abstract | Video
June 30, 2020Pete Casazza (University of Missouri): "Two Distance Sets" Abstract | Video
June 23, 2020Alex Iosevich (University of Rochester): "On point configurations and frame theory" Abstract | Video | Slides
June 9, 2020Gene Kopp (University of Bristol): "SIC-POVM existence and the Stark conjectures" Abstract | Video
June 2, 2020Jameson Cahill (New Mexico State University): "Optimal Parseval Frames" Abstract | Video
May 26, 2020Chris Cox (Carnegie Mellon University / Iowa State University): "Nearly Orthogonal Vectors" Abstract | Video
May 19, 2020Hans Parshall (Ohio State University / Western Washington University): "Optimal Line Packings" Abstract | Video