2016/09/23 by Bárány, Imre, Solymosi, József · 2 citations
#Combinatorics (math.CO) #FOS: Mathematics #Spectral Theory (math.SP)
paper · doi:10.48550/arxiv.1609.07439
Gershgorin's famous circle theorem states that all eigenvalues of a square matrix lie in disks (called Gershgorin disks) around the diagonal elements. Here we show that if the matrix entries are non-negative and an eigenvalue has geometric multiplicity at least two, then this eigenvalue lies in a smaller disk. The proof uses geometric rearrangement inequalities on sums of higher dimensional real vectors which is another new result of this paper.