We design heuristic algorithms to construct Hadamard matrices with two circulant cores. This hard combinatorial problem can be formulated in terms of objective functions of several binary variables, so that heuristic methodologies can be used. Our algorithms are based on local and tabu search and they use information on the geometry of the objective function landscapes. In addition, we use the ...

As part of a survey of state-of-the-art kernel approximation algorithms, we present a new sampling algorithm for circulant matrix construction to perform fast kernel matrix inversion in kernel ridge regression, comparing theoretical and experimental performance of that of multilevel circulant kernel approximation, incomplete Cholesky decomposition, and random features, all recent advances in th...

We associate to any given circulant complex matrix C another one E(C) such that E(E(C)) = C∗ the transpose conjugate of C. All circulant Hadamard matrices of order 4 satisfy a condition C4 on their eigenvalues, namely, the absolute value of the sum of all eigenvalues is bounded above by 4. We prove by a “descent” that uses our operator E that the only circulant Hadamard matrices of order n > 4,...

In this paper, a new family of relative difference sets with parameters (m, n, k, λ) = ((q − 1)/(q − 1), 4(q− 1), q, q/4) is constructed where q is a 2-power. The construction is based on the technique used in [2]. By a similar method, we also construct some new circulant weighing matrices of order q where q is a 2-power, d is odd and d ≥ 5. Correspondence: S.L. Ma Department of Mathematics Nat...

In this talk we expose the results about infinite families of vertex critical r-dichromatic circulant tournaments for all r ≥ 3. The existence of these infinite families was conjectured by Neumann-Lara [6], who later proved it for all r ≥ 3 and r = 7. Using different methods we find explicit constructions of these infinite families for all r ≥ 3, including the case when r = 7, which complete th...

In this paper we exhibit infinite families of vertex critical r-dichromatic circulant tournaments for all r ≥ 3. The existence of these infinite families was conjectured by NeumannLara (7), who later proved it for all r ≥ 3 and r 6= 7. Using different methods we find explicit constructions of these infinite families for all r ≥ 3, including the case when r = 7, which complets the proof of the c...

Blur removal is an important problem in signal and image processing. The blurring matrices obtained by using the zero boundary condition (corresponding to assuming dark background outside the scene) are Toeplitz matrices for one-dimensional problems and block-Toeplitz–Toeplitzblock matrices for two-dimensional cases. They are computationally intensive to invert especially in the block case. If ...

Eigenvectors of a max-min matrix characterize stable states of the corresponding discrete-events system. Investigation of the max-min eigenvectors of a given matrix is therefore of a great practical importance. The eigenproblem in max-min algebra has been studied by many authors. Interesting results were found in describing the structure of the eigenspace, and algorithms for computing the maxim...

Kirchhoo's Matrix Tree Theorem permits the calculation of the number of spanning trees in any given graph G through the evaluation of the determinant of an associated matrix. In the case of some special graphs Boesch and Prodinger 9] have shown how to use properties of Chebyshev polyno-mials to evaluate the associated determinants and derive closed formulas for the number of spanning trees of g...

Circulant matrix embedding is one of the most popular and efficient methods for the exact generation of Gaussian stationary univariate series. Although the idea of circulant matrix embedding has also been used for the generation of Gaussian stationary random fields, there are many practical covariance structures of random fields where classical embedding methods break down. In this work, we pro...