Ryser's Conjecture under eigenvalue conditions

Luis H. Gallardo


We prove the nonexistence of a circulant Hadamard matrix $H$ of order $n$, under technical conditions

on the eigenvalues of $H$, when $n$ has only two odd prime divisors and in the general case. Main tool are appropriate

properties of the $n$-th cyclotomic polynomial.


Hadamard matrices, circulant matrices, eigenvalues, cyclotomic polynomials, congruences

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ISSN: 1331-0623 (Print), 1848-8013 (Online)