Invariant Approximations for Generalized I-Contractions

ABSTRACT

The paper discusses common fixed point theory for generalized I-contractions of Ciric and R-subweakly commuting maps. Various results on invariant approximations are obtained.     

Fixed Points of Quasi (f,g)-Nonexpansive Multivalued Mapping

Fixed point theorems for hybrid pair of single valued and multivalued R-subweakly commuting maps are proved.     

R‐weak commutativity,examples, and applications

The aim of this article is to define a new contraction and its variants in non‐Archimedean Menger probabilistic metric‐spaces, and utilize them to establish the existence of a combined common fixed point illustrating with examples. We also apply our result to integral type equations, Volterra type integral equations, damped harmonic oscillators, and nonlinear matrix equations.     

M-PM空间中反交换映像的公共不动点定理

在M-PM空间中引入了反交换映像的概念,并讨论了映像在反交换条件下的公共不动点的存在性及唯—性问题,同时将此结果推广到Fuzzy度量空间中,改进和推广了若干重要结论.     

An analytic framework for the two-dimensional infinite Toda hierarchy associated with a commutative algebra

Starting with the group of operators on a separable Hilbert space that differ from the identity by a trace-class operator, we construct a solution of the two-dimensional infinite Toda hierarchy associated with a maximal commutative subalgebra in complex k×k matrices. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 155, No. 1, pp. 177–192, April, 2008.     

Construction of GHZ-Like States for a Three-Particle (Spin 1/2) System

As the simultaneous eigenstates of a complete set of commuting observables (CSCO) consisting of threebody operators of the form σ1ασ2βσrsγ, the construction of entangled states for a three-particle system is investigated. It is shown that there exist 54 different sets of operators (each containing four commuting three-body operators with their product being -1) and any three members of each set constitute a CSCO. It is found that 54 different sets of maximally entangled states can be constructed, including the usual GHZ (Greenberg-Horne-Zeilinger) state as a special case. Once a preferential representation is adopted, all of them can be expressed as a GHZ-like form. Moreover, there also exist 18sets of partially entangled states, where only two particles are entangled.     

The Fredholm index of a pair of commuting operators

This paper concerns Fredholm theory in several variables, and its applications to Hilbert spaces of analytic functions. One feature is the introduction of ideas from commutative algebra to operator theory. Specifically, we introduce a method to calculate the Fredholm index of a pair of commuting operators. To achieve this, we define and study the Hilbert space analogs of Samuel multiplicities in commutative algebra. Then the theory is applied to the symmetric Fock space. In particular, our results imply a satisfactory answer to Arveson’s program on developing a Fredholm theory for pure d-contractions when d = 2, including both the Fredholmness problem and the calculation of indices. We also show that Arveson’s curvature invariant is in fact always equal to the Samuel multiplicity for an arbitrary pure d-contraction with finite defect rank. It follows that the curvature is a similarity invariant. Received: October 2004 Revision: May 2005 Accepted: May 2005 Partially supported by National Science Foundation Grant DMS 0400509.     

Bergman空间上κ阶斜Toeplitz算子

In this paper κ-order slant Toeplitz operator on the Bergman space is defined. Some properties like spectrum, commuting are discussed.     

On pointwise <Emphasis Type="Italic">R</Emphasis>-subweakly commuting maps and best approximations

The main purpose of this paper is to prove some common fixed point theorems for pointwise R-subweakly commuting maps on non-starshaped domains in P-normed spaces and locally convex topological vector spaces.As applications,invariant approximation results ale established.This work provides extension as well as substantial improvement of several results in the existing literature.