Search results for " Neumann"
showing 10 items of 45 documents
An existence result for a Neumann problem
2015
The main result of this paper deals with the existence of at least one positive solution for a second order Neumann boundary value problem. Such a result is obtained by using an abstract coincidence point theorem that allows to get our conclusion under non standard conditions on the nonlinearity.
A note on faithful traces on a von Neumann algebra
2009
In this short note we give some techniques for constructing, starting from a {\it sufficient} family $\mc F$ of semifinite or finite traces on a von Neumann algebra $\M$, a new trace which is faithful.
Quasi *-algebras of measurable operators
2009
Non-commutative $L^p$-spaces are shown to constitute examples of a class of Banach quasi *-algebras called CQ*-algebras. For $p\geq 2$ they are also proved to possess a {\em sufficient} family of bounded positive sesquilinear forms satisfying certain invariance properties. CQ *-algebras of measurable operators over a finite von Neumann algebra are also constructed and it is proven that any abstract CQ*-algebra $(\X,\Ao)$ possessing a sufficient family of bounded positive tracial sesquilinear forms can be represented as a CQ*-algebra of this type.
Nonexistence of global weak solutions for a nonlinear Schrodinger equation in an exterior domain
2020
We study the large-time behavior of solutions to the nonlinear exterior problem L u ( t , x ) = &kappa
Rings with algebraic n-engel elements
1994
(1994). Rings with algebraic n-engel elements. Communications in Algebra: Vol. 22, No. 5, pp. 1685-1701.
Possible extensions of the noncommutative integral
2011
In this paper we will discuss the problem of extending a trace σ defined on a dense von Neumann subalgebra \(\mathfrak{M}\) of a topological *-algebra \({\mathfrak{A}}\) to some subspaces of \({\mathfrak{A}}\). In particular, we will prove that extensions of the trace σ that go beyond the space L1(σ) really exist and we will explicitly construct one of these extensions. We will continue the analysis undertaken in Bongiorno et al. (Rocky Mt. J. Math. 40(6):1745–1777, 2010) on the general problem of extending positive linear functionals on a *-algebra.
Tomita—Takesaki Theory in Partial O*-Algebras
2002
This chapter is devoted to the development of the Tomita-Takesaki theory in partial O*-algebras. In Section 5.1, we introduce and investigate the notion of cyclic generalized vectors for a partial O*-algebra, generalizing that of cyclic vectors, and its commutants. Section 5.2 introduces the notion of a cyclic and separating system (M, λ, λ c ), which consists of a partial O*-algebra M, a cyclic generalized vector λ for M and the commutant λ c of λ. A cyclic and separating system (M, λ, λ c ) determines the cyclic and separating system ((M w ′ )′, λ cc , (λ cc ) c ) of the von Neumann algebra (M w ′ )′, and this makes it possible to develop the Tornita-Takesaki theory. Then λ can be extende…
A note on semifinite von Neumann algebras
2009
In this note we give some techniques for constructing a faithful semi finite trace on a semifinite von Neumann algebra.
MR3299506 Reviewed Rădulescu, Florin(I-ROME2) On unbounded, non-trivial Hochschild cohomology in finite von Neumann algebras and higher order Berezin…
2015
If (At)t>1 is a family of finite von Neumann algebras with a Chapman-Kolmogorov set of linear maps (symbol system) (Φs,t), and if αt:A→A are isomorphisms in a finite family of von Neumann algebras, the corresponding Hochschild cocycles are related to an obstruction to the deformation of the set of linear maps (Φs,t) in the corresponding Chapman-Kolmogorov system (Φs,t)˜ of completely positive maps. In this set-up, the author introduces an invariant (c,Z) for a finite von Neumann algebra M, consisting of a 2-Hochschild cohomology cocycle c and a coboundary unbounded operator Z for c. With some assumptions on c and Z=α+X+iY (α>0, Y is antisymmetric), the existence of an unbounded derivation δ…
MR3257881 Reviewed Hadwin, Don Approximate double commutants in von Neumann algebras and C∗-algebras. Oper. Matrices 8 (2014), no. 3, 623–633. (Revie…
2015
In this paper, the author proves an asymptotic version of the double commutant theorem, in a particular set-up of commutative C∗ -algebras. More precisely, he considers the relative approximate double commutant of a C ∗-algebra with unit, and, using a theorem of characterization for a commutative C∗-subalgebra with unit (inspired by a well-known result due to Kadison for a von Neumann sub-algebra of type I), and from a theorem based on a Machado result, he proves that if A is a commutative C∗-subalgebra of a C∗-algebra B centrally prime with unit, then A is equal to its relative approximate double commutant. In the case where B is a von Neumann algebra, a distance formula is found.