Open research questions in Matrix Theory and Algorithms
60 unresolved questions extracted from the limitations and future-work sections of 557 Matrix Theory and Algorithms papers in our library. Each links back to the study that raised it.
What the literature leaves open
Existing QCUR methods may suffer from heavy computational costs for large-scale quaternion problems. The need for a novel QCUR decomposition method that can efficiently handle large-scale quaternion matrices.
A Randomized CUR Decomposition Based on Real Projectors for Large-scale Quaternion Matrices · 2026 · DOIThere is a gap in the understanding of the geometric regularities of sequences of matrix spectra. The paper identifies the need to understand the systematic cancellations coming from the symmetries of the matrices.
The common invariant cone problem is known to be algorithmically undecidable for general families of matrices. There is a need for an efficient algorithm to solve the problem in many cases.
The paper is based on numerical experiments and does not provide a rigorous mathematical analysis of the results. The sample size is limited to the first 500 spectra associated with several intrinsically interesting sequences. The paper does not provide a systematic study of the behavior of matrix spectra associated with rational sequences.
Future research could involve a rigorous mathematical analysis of the results. The study could be extended to include a larger sample size and a more comprehensive analysis of the behavior of matrix spectra associated with rational sequences. Future research could also involve the development of new methods for analyzing the properties of rational sequences.
The paper does not provide a comprehensive comparison with existing methods. The approach is limited to unitary groups and may not be applicable to other compact groups.
Defining multiplication on kaiso complex numbers. Analyzing the properties of kaiso complex numbers in different contexts.
The lack of a unified algebraic framework for kaiso complex numbers. The need for a closed formula for the inversion parity.
Further research is needed to explore the applications of the new approach to Weingarten calculus. The approach can be extended to other compact groups and used to study their properties. The results can be used to develop new methods for calculating moments of Haar-distributed unitary matrices.
Further research is needed to fully understand the systematic cancellations coming from the symmetries of the matrices. The methods used in the paper may be applicable to other areas of mathematics. The paper's findings may be relevant to the study of symmetric functions and Hecke theory.
Solving the Hermitian positive definite systems, which are sparse but ill-conditioned, involves using iterative methods, such as Conjugate Gradient (CG), which are time-consuming and computationally expensive.
Further study of the properties of the Hilbert matrix. Application of the paper's techniques to other matrices. Exploration of the connections between the Hilbert matrix and other areas of mathematics.
A gap in the literature is identified, and the paper claims to contribute to the field.
The paper identifies a gap in the understanding of the Hilbert matrix. The paper aims to fill this gap by exploring new properties of the matrix.
In this work, we have illustrated how a class of NEPvs can be transformed into a NEP in a way that enables the use of NEP solvers. The transformation involves a polynomial system of equations that must be solved each time the NEP is accessed. We propose 123 BIT Numerical Mathematics (2026) 66:30 Page 23 of 26 30 Table 1 Performance metrics from the simulation. Each solve with the SMW formula involves six full-sized linear solves. One evaluation of G(λ) and H (λ) can be performed together using five linear solves. All linear solves are sparse.
From eigenvector nonlinearities with quadratic structure to eigenvalue nonlinearities with algebraic structure · 2026 · DOIExisting methods for solving the matrix equation AXB = C have high computational complexity and memory requirements. There is a need for an efficient method that can handle large-scale problems with structured or sparse coefficient matrices.
Quaternionic conjugate-gradient method for solving the matrix equation $$AXB=C$$ over generalized quaternions · 2026 · DOIFurther study on the applications of the dual C-S inverse and the special dual C-S inverse. Further study on the characterization of stronger i-EP matrices and stronger appreciable i-EP matrices.
The paper identifies a gap in the characterization of dual generalized inverses. The paper identifies a gap in the introduction of the dual C-S inverse and the special dual C-S inverse.
Future research can focus on improving the efficiency and scalability of the proposed approach. The applicability of the approach to other types of data and applications can be explored.
The lack of efficient homomorphic linear algebra algorithms is a significant gap in existing solutions. The proposed approach addresses this gap by using CKKS and BLAS.
Further evaluation of the HKT method on more complex geometries and problems. Development of new methods for overcoming the instability of the linear systems. Application of the HKT method to other fields such as acoustics, electromagnetics, and elasticity.
Efficient Krylov-regularization solvers for multiquadric RBF discretizations of the 3D Helmholtz equation · 2026 · DOIThe instability of the linear systems resulting from the use of MQ-RBFs. The need for efficient and accurate methods for solving the 3D Helmholtz equation in complex geometries and three-dimensional problems.
Efficient Krylov-regularization solvers for multiquadric RBF discretizations of the 3D Helmholtz equation · 2026 · DOIThe paper identifies a gap in the existing literature regarding the effectiveness of preconditioned LSQR with iterative refinement. The paper notes that the choice of preconditioner can significantly affect the accuracy of the solution.
The paper identifies a gap in the understanding of polynomial equations over matrices. The paper aims to fill this gap by studying the solution set S and calculating its dimension.
The complete characterization of the Kronecker structure of a matrix pencil perturbed by another pencil of rank one involves very involved conditions. There is a need to better understand the meaning of those conditions.
Bounds for the change of the Weyr characteristic of matrix pencils after 1-rank perturbations · 2026 · DOI
Most-cited papers in Matrix Theory and Algorithms
- The Levenberg–Marquardt method: an overview of modern convergence theories and more · Computational Optimization and Applications · 2024 · 100 citations
- One-way or two-way factor model for matrix sequences? · Journal of Econometrics · 2023 · 30 citations
- Column-orthogonal nearly strong orthogonal arrays · Journal of Statistical Planning and Inference · 2021 · 18 citations
- Delayed linear difference equations: The method of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>Ƶ</mml:mo></mml:math>-transform · Electronic journal of qualitative theory of differential equations · 2020 · 17 citations
- Factorial Invariance and Orthogonal Rotation · Multivariate Behavioral Research · 2020 · 14 citations
- The relaxed gradient based iterative algorithm for solving the generalized coupled complex conjugate and transpose Sylvester matrix equations · Automatika · 2024 · 5 citations
- What a Determinant's Derivative Knows: Jacobi's Formula and Newton's Identity for Matrix Traces in Lean 4 · Zenodo (CERN European Organization for Nuclear Research) · 2026 · 3 citations
- The Natural Components of a Regular Linear System · Oxford Bulletin of Economics and Statistics · 2026 · 3 citations
- (R, S) conjugate solution to coupled Sylvester complex matrix equations with conjugate of two unknowns · Automatika · 2022 · 3 citations
- A Block Conjugate Gradient Method for Quaternion Linear · Yüzüncü Yıl Üniversitesi Fen Bilimleri Enstitüsü Dergisi · 2023 · 3 citations
Most recent work
- What a Determinant's Derivative Knows: Jacobi's Formula and Newton's Identity for Matrix Traces in Lean 4 · Zenodo (CERN European Organization for Nuclear Research) · 2026
- The Natural Components of a Regular Linear System · Oxford Bulletin of Economics and Statistics · 2026
- Preconditioned generalized minimal residual method for quaternion linear systems with structured coefficient matrices and its applications · Numerical Algorithms · 2026
- Subdirect sums of Nearly-SDD matrices · Japan Journal of Industrial and Applied Mathematics · 2026
- An inertial-type parameterized Uzawa method for solving saddle point linear systems · Japan Journal of Industrial and Applied Mathematics · 2026
- On numerical computation of inverses and determinants for generalized anti-tridiagonal Hankel matrices · Journal of Computational and Applied Mathematics · 2026
- Fast Measure Modification of Orthogonal Polynomials via Matrices with Displacement or Hierarchical Off-Diagonal Low-Rank Structure · SIAM Journal on Scientific Computing · 2026
- Riemannian Barzilai–Borwein method for the hermitian quaternion eigenvalue problem · Numerical Algorithms · 2026
- Theoretical insights on the residual transformation from bi-conjugate gradient into bi-conjugate residual via a smoothing scheme · Japan Journal of Industrial and Applied Mathematics · 2026
- Extensions of generalized Drazin-Riesz inverses · The Journal of Analysis · 2026
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