Let A = D A + B be a block r × r, r ≥ 2, Hermitian matrix of order n, where D A is the block diagonal part of A. The main results of the paper are Theorems 2.1 and 2.2, which state the sharp inequalities
and analyze the equality cases. Some implications of these results are indicated. As applications, matrices occurring in spectral graph theory are considered, and new lower bounds on the chromatic number of a graph are obtained. Bibliography: 7 titles.
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Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 382, 2010, pp. 82–103.
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Kolotilina, L.Y. Inequalities for the extreme eigenvalues of block-partitioned Hermitian matrices with applications to spectral graph theory. J Math Sci 176, 44–56 (2011). https://doi.org/10.1007/s10958-011-0392-9
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DOI: https://doi.org/10.1007/s10958-011-0392-9