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Lower bounds for the Perron root of a sum of nonnegative matrices
L. Yu. Kolotilina St. Petersburg Department of V. A. Steklov Institute of Mathematics, Russian Academy of Sciences
Abstract:
Let
$A^{(l)}$ $(l=1,\dots,k)$ be
$n\times n$ nonnegative matrices with right and left Perron vectors
$u^{(l)}$ and
$v^{(l)}$, respectively, and let
$D^{(l)}$ and
$E^{(l)}$ $(l=1,\dots,k)$ be positive-definite diagonal matrices of the same order. Extending known results, under the assumption that
$$
u^{(1)}\circ v^{(1)}=\dots=u^{(k)}\circ v^{(k)}\ne0
$$
(where "
$\circ$" denotes the componentwise, i.e., the Hadamard product of vectors) but without requiring that the matrices
$A^{(l)}$ be irreducible, for the Perron root of the sum
$\sum^k_{l=1}D^{(l)}A^{(l)}E^{(l)}$ we derive a lower bound of the form
$$
\rho\left(\sum^k_{l=1}D^{(l)}A^{(l)}E^{(l)}\right)\ge\sum^{k}_{l=1}\beta_l\rho(A^{(l)}),\quad\beta_l>0.
$$
Also we prove that, for arbitrary irreducible nonnegative matrices
$A^{(l)}$ $(l=1,\ldots,k)$,
$$
\rho\left(\sum^{k}_{l=1}A^{(l)}\right)\ge\sum^k_{l=1}\alpha_l\rho(A^{(l)}),
$$
where the coefficients
$\alpha_l>0$ are specified using an arbitrarily chosen normalized positive vector. The cases of equality in both estimates are analyzed, and some other related results are established.
UDC:
512.643 Received: 20.01.2000