L_∞ norm minimization for nowhere-zero integer eigenvectors of the block graphs of Steiner triple systems and Johnson graphs

04/03/2023

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by   E. A. Bespalov, et al.

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We study nowhere-zero integer eigenvectors of the block graphs of Steiner triple systems and the Johnson graphs. For the first eigenvalue we obtain the minimums of L_∞-norm for several infinite series of Johnson graphs, including J(n,3) as well as general upper and lower bounds. The minimization of L_∞-norm for nowhere-zero integer eigenvectors with the second eigenvalue of the block graph of a Steiner triple system S is equivalent to finding the minimum nowhere-zero flow for Steiner triple system S. For the all Assmuss-Mattson Steiner triple systems of order at least 99 we prove that this minimum is bounded above by 4.