Graphs and Hermitian matrices: discrepancy and singular values
arXiv:math/0404559
Abstract
We introduce a measure of discrepancy of Hermitian matrices and establish an inequality between the second singular value of a Hermitian matrix and its discrepancy. These results are applied to answer two questions of Fan Chung about graph eigenvalues.
22 pages, accepted in Discrete Math. Rev 2 - some typos corrected, thanks Herbert Wilf