[HTML][HTML] Spherical (t, t)-designs with a small number of vectors

D Hughes, S Waldron - Linear Algebra and its Applications, 2021 - Elsevier
Abstract For t∈{1, 2,…} fixed, a natural class of spherical designs is given by the vectors v
1,…, vn in F d= R d, C d (not all zero) which give equality in the bound∑ j= 1 n∑ k= 1 n|< vj …

Biangular Gabor frames and Zauner's conjecture

M Magsino, DG Mixon - Wavelets and Sparsity XVIII, 2019 - spiedigitallibrary.org
Two decades ago, Zauner conjectured that for every dimension d, there exists an
equiangular tight frame consisting of d 2 vectors in C d. Most progress to date explicitly …

Symplectic geometry and connectivity of spaces of frames

T Needham, C Shonkwiler - Advances in Computational Mathematics, 2021 - Springer
Frames provide redundant, stable representations of data which have important applications
in signal processing. We introduce a connection between symplectic geometry and frame …

Admissibility and frame homotopy for quaternionic frames

T Needham, C Shonkwiler - Linear Algebra and its Applications, 2022 - Elsevier
We consider the following questions: when do there exist quaternionic frames with given
frame spectrum and given frame vector norms? When such frames exist, is it always …

Toric symplectic geometry and full spark frames

T Needham, C Shonkwiler - Applied and Computational Harmonic Analysis, 2022 - Elsevier
The collection of d× N complex matrices with prescribed column norms and singular values
forms an algebraic variety, which we refer to as a frame space. Elements of frame spaces …

On the search for tight frames of low coherence

X Chen, DP Hardin, EB Saff - Journal of Fourier Analysis and Applications, 2021 - Springer
We introduce a projective Riesz s-kernel for the unit sphere S^ d-1 S d-1 and investigate
properties of N-point energy minimizing configurations for such a kernel. We show that these …

Lie PCA: Density estimation for symmetric manifolds

J Cahill, DG Mixon, H Parshall - Applied and Computational Harmonic …, 2023 - Elsevier
We introduce an extension to local principal component analysis for learning symmetric
manifolds. In particular, we use a spectral method to approximate the Lie algebra …

Geometric Approaches to Matrix Normalization and Graph Balancing

T Needham, C Shonkwiler - arxiv preprint arxiv:2405.06190, 2024 - arxiv.org
Normal matrices, or matrices which commute with their adjoints, are of fundamental
importance in pure and applied mathematics. In this paper, we study a natural functional on …

Fusion frame homotopy and tightening fusion frames by gradient descent

T Needham, C Shonkwiler - Journal of Fourier Analysis and Applications, 2023 - Springer
Finite frames, or spanning sets for finite-dimensional Hilbert spaces, are a ubiquitous tool in
signal processing. There has been much recent work on understanding the global structure …

Feichtinger Conjectures, -Conjectures and Weaver's Conjectures for Banach spaces

KM Krishna - arxiv preprint arxiv:2201.00125, 2022 - arxiv.org
Motivated from two decades old famous Feichtinger conjectures for frames, $ R_\varepsilon
$-conjecture and Weaver's conjecture for Hilbert spaces (and their solution by Marcus …