60,495 research outputs found
On accuracy of approximation of the spectral radius by the Gelfand formula
The famous Gelfand formula for
the spectral radius of a matrix is of great importance in various mathematical
constructions. Unfortunately, the range of applicability of this formula is
substantially restricted by a lack of estimates for the rate of convergence of
the quantities to . In the paper this deficiency is
made up to some extent. By using the Bochi inequalities we establish explicit
computable estimates for the rate of convergence of the quantities
to . The obtained estimates are then extended for
evaluation of the joint spectral radius of matrix sets.Comment: Corrected typos, improved estimate for the kay constant in the paper,
added reference
A relaxation scheme for computation of the joint spectral radius of matrix sets
The problem of computation of the joint (generalized) spectral radius of
matrix sets has been discussed in a number of publications. In the paper an
iteration procedure is considered that allows to build numerically Barabanov
norms for the irreducible matrix sets and simultaneously to compute the joint
spectral radius of these sets.Comment: 16 pages, 2 figures, corrected typos, accepted for publication in
JDE
An explicit Lipschitz constant for the joint spectral radius
In 2002 F. Wirth has proved that the joint spectral radius of irreducible
compact sets of matrices is locally Lipschitz continuous as a function of the
matrix set. In the paper, an explicit formula for the related Lipschitz
constant is obtained.Comment: 9 pages, corrected typos and reference
A Sub-Neptune-sized Planet Transiting the M2.5 Dwarf G 9-40: Validation with the Habitable-zone Planet Finder
We validate the discovery of a 2-Earth-radii sub-Neptune-sized planet around the nearby high-proper-motion M2.5 dwarf G 9-40 (EPIC 212048748), using high-precision, near-infrared (NIR) radial velocity (RV) observations with the Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based photometry with a custom narrowband photometric filter, and adaptive optics imaging. At a distance of d = 27.9 pc, G 9-40b is the second-closest transiting planet discovered by K2 to date. The planet's large transit depth (~3500 ppm), combined with the proximity and brightness of the host star at NIR wavelengths (J = 10, K = 9.2), makes G 9-40b one of the most favorable sub-Neptune-sized planets orbiting an M dwarf for transmission spectroscopy with James Webb Space Telescope, ARIEL, and the upcoming Extremely Large Telescopes. The star is relatively inactive with a rotation period of ~29 days determined from the K2 photometry. To estimate spectroscopic stellar parameters, we describe our implementation of an empirical spectral-matching algorithm using the high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective temperature of
T_(eff) = 3404±73K, and metallicity of [Fe/H] = −0.08±0.13. Our RVs, when coupled with the orbital parameters derived from the transit photometry, exclude planet masses above 11.7M⊕ with 99.7% confidence assuming a circular orbit. From its radius, we predict a mass of M = 5.0^(+3.8)_(−1.9) M⊕ and an RV semiamplitude of K = 4.1^(+3.1)_(−1.6) ms⁻¹, making its mass measurable with current RV facilities. We urge further RV follow-up observations to precisely measure its mass, to enable precise transmission spectroscopic measurements in the future
Iterative building of Barabanov norms and computation of the joint spectral radius for matrix sets
The problem of construction of Barabanov norms for analysis of properties of
the joint (generalized) spectral radius of matrix sets has been discussed in a
number of publications. The method of Barabanov norms was the key instrument in
disproving the Lagarias-Wang Finiteness Conjecture. The related constructions
were essentially based on the study of the geometrical properties of the unit
balls of some specific Barabanov norms. In this context the situation when one
fails to find among current publications any detailed analysis of the
geometrical properties of the unit balls of Barabanov norms looks a bit
paradoxical. Partially this is explained by the fact that Barabanov norms are
defined nonconstructively, by an implicit procedure. So, even in simplest cases
it is very difficult to visualize the shape of their unit balls. The present
work may be treated as the first step to make up this deficiency. In the paper
two iteration procedure are considered that allow to build numerically
Barabanov norms for the irreducible matrix sets and simultaneously to compute
the joint spectral radius of these sets.Comment: 17 pages, 36 bibliography references, 3 figures; shortened version,
new LaTeX style, fixed typos, accepted in DCDS-
Tropical Kraus maps for optimal control of switched systems
Kraus maps (completely positive trace preserving maps) arise classically in
quantum information, as they describe the evolution of noncommutative
probability measures. We introduce tropical analogues of Kraus maps, obtained
by replacing the addition of positive semidefinite matrices by a multivalued
supremum with respect to the L\"owner order. We show that non-linear
eigenvectors of tropical Kraus maps determine piecewise quadratic
approximations of the value functions of switched optimal control problems.
This leads to a new approximation method, which we illustrate by two
applications: 1) approximating the joint spectral radius, 2) computing
approximate solutions of Hamilton-Jacobi PDE arising from a class of switched
linear quadratic problems studied previously by McEneaney. We report numerical
experiments, indicating a major improvement in terms of scalability by
comparison with earlier numerical schemes, owing to the "LMI-free" nature of
our method.Comment: 15 page
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