Search results for "MATEMATICA"
showing 10 items of 1637 documents
An existence result for a class of variational inequalities with L^1 data
2001
existence result
MR2661185 Reviewed Huang, Xianjiu; Zhu, Chuanxi; Wen, Xi Common fixed point theorem for four non-self-mappings in cone metric spaces. Fixed Point The…
2012
Recently, L. G. Huang and X. Zhang [J. Math. Anal. Appl. 332 (2007), no. 2, 1468–1476; MR2324351 (2008d:47111)] defined cone metric spaces by substituting an order normed space for the real numbers and proved some fixed point theorems. In this paper the authors prove a common fixed point theorem for four non-self-mappings in the framework of cone metric spaces. This result is an extension of a common fixed point theorem of Radenović and Rhoades for two non-self-mappings. The paper also contains some illustrative examples. For fixed point results in the framework of cone metric spaces see also [M. Arshad, A. Azam and P. Vetro, Fixed Point Theory Appl. 2009, Art. ID 493965; MR2501489 (2010e:5…
MR3586679 Reviewed Maksimović, Snježana(BS-BALUEL); Mincheva-Kamińska, Svetlana(PL-RZSZM); Pilipović, Stevan(SE-NOVIS-NDM); Sokoloski, Petar(MK-SKOPN…
2017
The purpose of the paper is to investigate ultradistributions of both Beurling and Roumieu (briefly, B and R) types with the help of a sequential approach, considering certain equivalence classes of fundamental sequences of smooth functions defined by ultradifferential operators. More precisely, the authors define as s-ultradistributions the equivalence classes U(t) and U{t} of B and R types respectively on test functions belonging respectively to D′(t)(Ω) and D′{t}(Ω) on the open set Ω⊂Rn, and T(t), T{t}, T~(t) and T~{t} of (tempered) t- and t~-distributions, and study their properties. Finally, the authors prove the existence of topological isomorphism between the classes T(t), T{t}, T~(t…
MR3730338 Reviewed de Jeu, Marcel(NL-LEID-MI); Tomiyama, Jun(J-TOKYM) The closure of ideals of ℓ1(Σ) in its enveloping C∗-algebra. (English summary) …
2018
Given a compact Hausdorff space X and a homeomorphism σ on X, denote by Σ=(X,σ) a topological dynamical system. Then the associated Banach ∗-algebra ℓ1(Σ) is defined as ℓ1(Σ)={a:Z→C(X), ∥a∥:=∑n∈Z∥a(n)∥<∞} with a crossed product–type product (aa′)(n)=∑k∈Za(k)⋅αk(a′(n−k)) and involution a∗(n)=αn(a(−n))¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯, where C(X) denote the space of complex-valued continuous functions on X, and α(f):=f∘σ−1 for f∈C(X). If C∗(Σ) is the enveloping C∗-algebra of ℓ1(Σ), considering a primitive ideal I of ℓ1(Σ), the authors show that there exists a ∗-representation π of ℓ1(Σ) on Hilbert space such that the kernel is I, and that the closure in C∗(Σ) of an ideal of ℓ1(Σ) is an ideal of C∗(Σ).
On k-ball contractive retractions in F-normed ideal spaces
2010
Let X be an infinite dimensional F-normed space and r a positive number such that the closed ball B_r(X) of radius r is properly contained in X. For a bounded subset A of X, the Hausdorff measure of noncompactness gamma(A) of A is the infimum of all $\eps >0$ such that A has a finite $\eps$-net in X. A retraction R of B_r(X) onto its boundary is called k-ball contractive if $\gamma(RA) \le k \gamma(A)$ for each subset A of B_r(X). The main aim of this talk is to give examples of regular F-normed ideal spaces in which there is a 1-ball contractive retraction or, for any $\eps>0$, a $(1+ \eps)$-ball contractive retraction with positive lower Hausdorff measure of noncompactness.
A fixed point theorem for uniformly locally contractive mappings in a C-chainable cone rectangular metric space
2011
Recently, Azam, Arshad and Beg [ Banach contraction principle on cone rectangular metric spaces, Appl. Anal. Discrete Math. 2009] introduced the notion of cone rectangular metric spaces by replacing the triangular inequality of a cone metric space by a rectangular inequality. In this paper, we introduce the notion of c-chainable cone rectangular metric space and we establish a fixed point theorem for uniformly locally contractive mappings in such spaces. An example is given to illustrate our obtained result.
A decomposition theorem for σ-P-directionally porous sets in Fréchet spaces
2007
In this paper we study suitable notions of porosity and directional porosity in Fréchet spaces. Moreover we give a decomposition theorem for $\sigma$-$\mathcal{P}$-directionally porous sets.
MR3112896 Saichev, Alexander I.; Woyczyński, Wojbor A. Distributions in the physical and engineering sciences. Vol. 2. Linear and nonlinear dynamics …
2014
Locally Convex Quasi *-Algebras and their Representations
2020
This book is a review of the work the authors have done in the past 20 years on the theory of locally convex quasi *-algebras