On Hadamard Matrices at Roots of Unity
نویسنده
چکیده
Abstract. We study Hadamard matrices of order n, formed by l-th roots of unity. A main problem is to find the allowed values of (n, l), and we discuss here the following statement: for l = pa 1 . . . pa s we must have n ∈ p1+. . .+psN. For s = 1 this is a previously known result, for s = 2, 3 this is a result that we prove in this paper, and for s ≥ 4 this is a conjecture that we raise. We present as well some remarks and comments regarding the other known obstructions.
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