Search results for "RANK"
showing 10 items of 1387 documents
Property (w) for perturbations of polaroid operators
2008
Abstract A bounded linear operator T ∈ L ( X ) acting on a Banach space satisfies property ( w ) , a variant of Weyl’s theorem, if the complement in the approximate point spectrum σ a ( T ) of the Weyl essential approximate-point spectrum σ wa ( T ) is the set of all isolated points of the spectrum which are eigenvalues of finite multiplicity. In this note, we study the stability of property ( w ) for a polaroid operator T acting on a Banach space, under perturbations by finite rank operators, by nilpotent operators and, more generally, by algebraic operators commuting with T.
Operators which have a closed quasi-nilpotent part
2002
We find several conditions for the quasi-nilpotent part of a bounded operator acting on a Banach space to be closed. Most of these conditions are established for semi-Fredholm operators or, more generally, for operators which admit a generalized Kato decomposition. For these operators the property of having a closed quasi-nilpotent part is related to the so-called single valued extension property.
Evolution semigroups and time operators on Banach spaces
2010
AbstractWe present new general methods to obtain shift representation of evolution semigroups defined on Banach spaces. We introduce the notion of time operator associated with a generalized shift on a Banach space and give some conditions under which time operators can be defined on an arbitrary Banach space. We also tackle the problem of scaling of time operators and obtain a general result about the existence of time operators on Banach spaces satisfying some geometric conditions. The last part of the paper contains some examples of explicit constructions of time operators on function spaces.
Classical operators on weighted Banach spaces of entire functions
2013
We study the operators of differentiation and of integration and the Hardy operator on weighted Banach spaces of entire functions. We estimate the norm of the operators, study the spectrum, and analyze when they are surjective, power bounded, hypercyclic, and (uniformly) mean ergodic.
Spectra and essential spectral radii of composition operators on weighted Banach spaces of analytic functions
2008
AbstractWe determine the spectra of composition operators acting on weighted Banach spaces Hv∞ of analytic functions on the unit disc defined for a radial weight v, when the symbol of the operator has a fixed point in the open unit disc. We also investigate in this case the growth rate of the Koenigs eigenfunction and its relation with the essential spectral radius of the composition operator.
Operator martingale decomposition and the Radon-Nikodym property in Banach spaces
2010
Abstract We consider submartingales and uniform amarts of maps acting between a Banach lattice and a Banach lattice or a Banach space. In this measure-free setting of martingale theory, it is known that a Banach space Y has the Radon–Nikodým property if and only if every uniformly norm bounded martingale defined on the Chaney–Schaefer l-tensor product E ⊗ ˜ l Y , where E is a suitable Banach lattice, is norm convergent. We present applications of this result. Firstly, an analogues characterization for Banach lattices Y with the Radon–Nikodým property is given in terms of a suitable set of submartingales (supermartingales) on E ⊗ ˜ l Y . Secondly, we derive a Riesz decomposition for uniform …
Factors Differentiating Rural and Urban Population in Determining Anxiety and Depression in Patients with Chronic Cardiovascular Disease: A Pilot Stu…
2021
The aim of this cross-sectional study was to analyze selected variables differentiating rural from urban populations, as well as identify potentially increased levels of depression and anxiety in patients with chronic cardiovascular disease. The study was carried out in 193 patients. The study used the Camberwell Assessment of Need Short Appraisal Schedule (CANSAS), the Health Behavior Inventory Questionnaire (HBI), the WHOQOL-BREF Quality of Life Questionnaire, and the Hospital Anxiety and Depression Scale–Modified Version (HADS-M). Spearman’s rank correlation coefficient test and logistic regression were used for analyses. In rural patients, we observed a relationship between anxiety and …
The Urban Park as a "Social Island". The ANP in the Participatory Project of Parco Uditore in Palermo
2019
An urban park provides many environmental and recreational facilities and services, and moreover it may become a catalyst for social energies and an instrument of community identification. This paper analyses whether participation and bottom-up planning may compensate institutional absences in implementation of urban parks, and how multiple criteria model may support socially shared decisions about their management. These issues are examined from the singular case of Parco Uditore in Palermo (Italy) that is located in a land which has been surprisingly undeveloped, despite the expansion of the city. The phases of promotion, planning and implementation of the park were the result of a synerg…
Cities, hinterlands and agglomeration shadows: spatial developments in Finland over 1880-2004
2011
This paper analyzes long-term spatial developments in Finland by focusing on two predictions of the new economic geography (NEG) models, the increasing persistence of locational patterns and the emerging agglomeration shadow, i.e. the rising dominance of growth centers. Pre- and post-war periods are distinguished to roughly express the shift from an agriculture-based economy to a post-industrial country. The analyses base on the assumption that each of the 19 Finnish regions has a center of its own and the rest of the region forms its local hinterland. The empirical analysis is based on regional population data from 1880 to 2004 at decade intervals. First, to analyze the persistence of loca…