56 citations · 276 across the 24 of their papers we have counts for
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Extended double covers of non-symmetric association schemes of class
Takuya Ikuta, Akihiro Munemasa
In this paper, we give a method to construct non-symmetric association schemes of class from non-symmetric association schemes of class . This construction is a non-symmetri…
Bordered complex Hadamard matrices and strongly regular graphs
Takuya Ikuta, Akihiro Munemasa
We consider bordered complex Hadamard matrices whose core is contained in the Bose-Mesner algebra of a strongly regular graph. Examples include a complex Hadamard matrix whose core…
Complex Hadamard matrices attached to a 3-class nonsymmetric association scheme
Takuya Ikuta, Akihiro Munemasa
In this paper we classify complex Hadamard matrices contained in the Bose-Mesner algebra of nonsymmetric 3-class association schemes. As a consequence of our classification, we hav…
Butson-type complex Hadamard matrices and association schemes on Galois rings of characteristic 4
Takuya Ikuta, Akihiro Munemasa
We consider nonsymmetric hermitian complex Hadamard matrices belonging to the Bose-Mesner algebra of commutative nonsymmetric association schemes. First, we give a characterization…
Complex Hadamard matrices attached to even orthogonal schemes of class 4
Takuya Ikuta, Akihiro Munemasa
A complex Hadamard matrix is a square matrix W with complex entries of absolute value 1 satisfying WW*=nI, where * stands for the Hermitian transpose and I is the identity matrix o…
Complex Hadamard matrices contained in a Bose-Mesner algebra
Takuya Ikuta, Akihiro Munemasa
A complex Hadamard matrix is a square matrix H with complex entries of absolute value 1 satisfying , where stands for the Hermitian transpose and I is the identity ma…
Nomura algebras of nonsymmetric Hadamard models
Takuya Ikuta, Akihiro Munemasa
We show that the Nomura algebra of the nonsymmetric Hadamard model coincides with the Bose-Mesner algebra of the directed Hadamard graph.
Spin models constructed from Hadamard matrices
Takuya Ikuta, Akihiro Munemasa
A spin model (for link invariants) is a square matrix which satisfies certain axioms. For a spin model , it is known that is a permutation matrix, and its order…
Pseudocyclic association schemes and strongly regular graphs
Akihiro Munemasa, Takuya Ikuta
Let X be a pseudocyclic association scheme in which all the nontrivial relations are strongly regular graphs with the same eigenvalues. We prove that the principal part of the firs…