7 citations · 19 across the 13 of their papers we have counts for
12 papers · 1 filter
A generalisation of bent vectors for Butson Hadamard matrices
José Andrés Armario, Ronan Egan, Hadi Kharaghani +1
An complex matrix with entries in the roots of unity which satisfies is called a Butson Hadamard matrix. While a matrix with…
Generalized partially bent functions, generalized perfect arrays and cocyclic Butson matrices
José Andrés Armario, Ronan Egan, Dane Flannery
In a recent survey, Schmidt compiled equivalences between generalized bent functions, group invariant Butson Hadamard matrices, and abelian splitting relative difference sets. We e…
Almost supplementary difference sets and quaternary sequences
J. A. Armario, D. L. Flannery
We introduce almost supplementary difference sets (ASDS). For odd , certain ASDS in that have amicable incidence matrices are equivalent to quaternary sequences…
Generalized Hadamard full propelinear codes
José Andrés Armario, Ivan Bailera, Ronan Egan
Codes from generalized Hadamard matrices have already been introduced. Here we deal with these codes when the generalized Hadamard matrices are cocyclic. As a consequence, a new cl…
Generalized binary arrays from quasi-orthogonal cocycles
J. A. Armario, D. L. Flannery
Generalized perfect binary arrays (GPBAs) were used by Jedwab to construct perfect binary arrays. A non-trivial GPBA can exist only if its energy is or a multiple of . This…
On quasi-orthogonal cocycles
J. A. Armario, D. L. Flannery
We introduce the notion of quasi-orthogonal cocycle. This is motivated in part by the maximal determinant problem for square -matrices of size congruent to modulo $4…
Gröbner bases and cocyclic Hadamard matrices
V. Álvarez, J. A. Armario, R. M. Falcón +2
Hadamard ideals were introduced in 2006 as a set of nonlinear polynomial equations whose zeros are uniquely related to Hadamard matrices with one or two circulant cores of a given…
Determinants of -matrices of the skew-symmetric type: a cocyclic approach
V. Álvarez, J. A. Armario, M. D. Frau +1
An by skew-symmetric type -matrix has 's on the main diagonal and 's elsewhere with . The largest possible determinant of…
On permanents of Sylvester Hadamard matrices
José Andrés Armario
It is well-known that the evaluation of the permanent of an arbitrary -matrix is a formidable problem. Ryser's formula is one of the fastest known general algorithms for co…
GA based robust blind digital watermarking
Víctor Álvarez, José-Andrés Armario, María-Dolores Frau +4
A genetic algorithm based robust blind digital watermarking scheme is presented. Starting from a binary image (the original watermark), a genetic algorithm is performed searching f…
Embedding cocyclic D-optimal designs in cocyclic Hadamard matrices
Víctor Álvarez, José-Andrés Armario, María-Dolores Frau +1
In this paper a method for embedding cocyclic submatrices with ``large'' determinants of orders 2t in certain cocyclic Hadamard matrices of orders 4t is described (t an odd integer…
Searching for partial Hadamard matrices
Víctor Álvarez, José-Andrés Armario, María-Dolores Frau +4
Three algorithms looking for pretty large partial Hadamard matrices are described. Here "large" means that hopefully about a third of a Hadamard matrix (which is the best asymptoti…