1,721,015 research outputs found
CQ -algebras of measurable operators
Full text linkWe study, from a quite general point of view, a CQ*-algebra (X, A0) possessing a sufficient family
of bounded positive tracial sesquilinear forms. Non-commutative L^2 -spaces are shown to constitute examples
of a class of CQ*-algebras and any abstract CQ*-algebra (X, A0) possessing a sufficient family of bounded
positive tracial sesquilinear forms can be represented as a direct sum of non-commutative L^2-spaces
A note on states and traces from biorthogonal sets
Full text linkIn this paper, following Bagarello, Trapani, and myself, we generalize the Gibbs states and their related KMS-like conditions. We have assumed that H0, H are closed and, at least, densely defined, without giving information on the domain of these operators. The problem we address in this paper is therefore to find a dense domain D that allows us to generalize the states of Gibbs and take them in their natural environment i.e., defined in L†(D)
Some classes of quasi *-algebras
Full text linkIn this paper we will continue the analysis undertaken in [1] and in [2] [20] our investigation on the structure of Quasi-local quasi *-algebras possessing a sufficient family of bounded positive tracial sesquilinear forms. In this paper it is shown that any Quasi-local quasi *-algebras (A, A0), possessing a ”sufficient state” can be represented as non-commutative L2- spaces
Local spectral theory for r and s satisfying rnsrn = rj
Full text linkIn this paper, we analyze local spectral properties of operators R, S and RS which satisfy the operator equations RnSRn = Rj and Sn RSn = Sj for same integers j ≥ n ≥ 0. We also continue to study the relationship between the local spectral properties of an operator R and the local spectral properties of S. Thus, we investigate the transmission of some local spectral properties from R to S and we illustrate our results with an example. The theory is exemplified in some cases
Some Remarks on the Spectral Properties of Toeplitz Operators
Full text linkIn this paper, we study some local spectral properties of Toeplitz operators T-phi defined on Hardy spaces, as the localized single-valued extension property and the property of being hereditarily polaroid
Un modello di distribuzione e idoneità ambientale di una specie steppica in pericolo: dell’occhione Burhinus oedicnemus
No full textSesquilinear forms as eigenvectors in quasi *-algebras, with an application to ladder elements
Full text linkWe consider a particular class of sesquilinear forms on a Banach quasi *-algebra (A[parallel to.parallel to],A0[parallel to.parallel to 0]) that we call eigenstates of an element a is an element of A, and we deduce some of their properties. We further apply our definition to a family of ladder elements, that is, elements of A obeying certain commutation relations physically motivated, and we discuss several results, including orthogonality and biorthogonality of the forms, via Gelfand-Naimark-Segal (GNS) representation
Limits of hypercyclic operators on Hilbert spaces
Full text linkThis article concerns the operators T E L(H), defined on a separable Hilbert space H, that belong to the norm closure HC(H) in L(H) of the set HC(H) of all hypercyclic operators. Starting from a Herrero's characterization of these operators [11] we deduce some criteria that are very useful in many concrete cases. We also show that if T E L(H) is invertible then T E HC(H) if and only if T-1 E HC(H). This result extends to HC(H) a known result of Kitai and Herrero established for hypercyclic operators, ([13]). (c) 2025 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Bollettino di matematica pura e applicata. Vol. 11: Atti dell'International Conference on Topological Algebras and Their Applications (ICTAA) 2022
No full textThe papers injcluded in this volume contain the contributions given by several participants to the
International Conference on Topological Algebras and Applications (ICTAA2022) organized on
line by the Department of Mathematics and Computer Science of Palermo University (Italy) in
the period August 31 - September 2, 2022.
The conference was expected to be attended in presence but the aftermath of the COVID19
pandemic and the general political situation suggested converting this event to an online meeting.
ICTAA2022 has been the thirteenth of a series begun in 1999 in Tartu (Estonia). The subjects
covered in the conference were the traditional ones: Categories of Topological Algebras,
Topological Rings, Topological Linear Spaces, Topological Modules, Topological Groups and
Semigroups, Bornological Structures, Sheaf Theory, Bundle Theory, Topological K-theory,
Operator algebras etc.
Thirty mathematicians, from thirteen countries, participated to the meeting and almost all
presented the results of their recent research during the meeting.
We thank all participants and speakers for their cooperation in making of ICTAA2022 a successful
event from the scientific point of view.
Unfortunately, all the aspects of sociability that usually accompany a conference were missing,
but this did not depend on the will of the organizers or on that one of the participants.
We hope that the next ICTAA will be a real occasion of meeting personally old and new colleagues
and friends working in the field of Topological Algebras and Applications.
A special thank is due to Dr. Giuseppe Russo for his technical help which made possible the
organization of ICTAA2022 on-lin
Un modello di distribuzione e idoneità ambientale di una specie steppica in pericolo: l’Occhione Burhinus oedicnemus
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